Tag Archives: Solitude Lake Management

Property Owner Association Uses Hydrographic & Sediment Surveys to Create Strategic Sediment Removal Plan – Resulting in Hundreds of Thousands in Savings

The Mapping Network Hydrographic Survey Team exceeds expectations for Property Owner Association.

Overview:  A lake property association (POA) has been dealing directly with the challenges associated with sedimentation in their lakes for over 20 years.  In 2002 The Board of Directors created a 30 year sediment removal and management plan (2002-2031).  They looked at 3 different options: A) hiring a dredging professional, B) leasing dredging equipment and use current POA staff to operate, or C) purchasing a new dredge and using POA staff to operate.  They contacted two environmental consultants for cost estimates over the 30 year process.  The estimates ranged from $1,000,000 to $5,000,000 which left the POA in a difficult position of trying to make a long term management decision based on wide ranging potential costs.  In the end the POA decided to purchase their own dredging equipment an utilize existing staff and volunteers to operated the equipment.

In House Accountability Challenges:  After nearly a decade of in house dredging the POA Board of Directors was unable to quantify and verify results.  When reviewing the budget requests from the lakes and dam committee, they realized they were spending a lot of resources without having clear information on how successful the sediment removal process had been over the years.

New Vision:  The POA decided they needed to quantify the sediment problem to create a sustainable sediment management plan.  The president of the board spearheaded an effort to get a hydrographic and sediment survey completed.  The president contacted several hydrographic survey companies and chose The Mapping Network to provide this service based on experience in the industry and listening to the needs of the POA.

Lake Survey Purpose:  The primary objective of the hydrographic and sediment survey was to better understand the condition of the lake by charting the existing lake contours along with mapping the sediment thickness throughout the lake.  Once the mapping process was completed the POA was able to identify areas that needed dredging and how much material was there.  This allows for much better budgeting and accountability.

Results: The POA was excited to have information based on real numbers (lake and sediment survey).  The hydrographic survey results are an essential part of the decision making process with regards to the sediment removal planning.  After 20 years of dredging and several studies performed by consultants they felt for the first time they finally understood the problem and how to manage it.  Now they have real information, which gives them a clear picture of what to do in the future.

Future: Members of the POA say they will completely change course by finishing up the current in house dredging work and then sell all dredging equipment.  They will then work with a  professional dredging contractor to clean out specified problem areas identified during the hydrographic survey process.  Understanding the true extent of the lake sediment distribution in the lake will save the POA an estimated $200,000 to $300,000 in costs by selling unnecessary equipment and strategic dredging planning.  The POA will be using the hydrographic survey information as a baseline for all future work and will adjust the map as dredging continues.

Conclusion:  In the end the primary problem facing the POA was not the sediment in the lake but rather not knowing the facts about the lake to make the best decisions.  The POA now has the facts needed to create a comprehensive plan that will accurately represent the work being completed.  Plus members have a wonderful contour map to assist with fishing!

The Mapping Network surveyed the bottom of the lake including the sediment depths. This map shows the lake water depth as blue contours lines as well as a color shaded sediment thickness. This specialized technology allows the POA to easily locate problem areas.

The Mapping Network surveyed the bottom of the lake including the sediment depths. This map shows the lake water depth as blue contours lines as well as a color shaded sediment thickness. This specialized technology allows the POA to easily locate problem areas.

The Mapping Network is an industry leader in Hydrographic Surveys, Bathymetry, Geographic Information Systems Consulting, Data Conversion, and GPS Data Collection.  We specialize in terrain and sub-surface (bathymetry) GPS mapping.   If you are serious about maintaining  a high-quality golf course, lake or pond, be sure you have the ability to make the best decisions,  get your resource mapped by the professionals at The Mapping Network.   Give us a call or send an e-mail to find out more details.

phone:  (402) 241-8177

e-mail: info@themappingnetwork.com

website: www.themappingnetwork.com

Check out The Mapping Network on Facebook for more examples and success stories!

The Mapping Network is proud to announce their firm has been chosen by Cabela’s, the World’s Foremost Outfitter, as a Landowner Services provider for Cabela’s Trophy Properties throughout the United States.  Visit us on the Cabela’s Trophy Properties website >> click here

The Mapping Network:  www.TheMappingNetwork.com

A Nationwide Network of GPS Mapping Professionals

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Property Owner Association Uses Hydrographic & Sediment Surveys to Create Strategic Sediment Removal Plan

The Mapping Network Hydrographic Survey Team exceeds expectations for Property Owner Association.

Sediment problems are inevitable in all lakes and at some point removal is required.  Lake dredging and/or excavation can be an expensive process and requires accurate planning to be as cost-efficient as possible.   A lake Property Owners Association (POA) had been dealing directly with the challenges associated with sedimentation in their lake.  The POA decided they needed to quantify the sediment problem to create a sustainable sediment management plan.  The president of the board spearheaded an effort to get a hydrographic and sediment survey completed.  The president contacted several hydrographic survey companies and chose The Mapping Network to provide this service based on experience in the industry and listening to the needs of the POA.

Lake Survey Purpose:  The primary objective of the hydrographic and sediment survey was to better understand the condition of the lake by charting the existing lake contours along with mapping the sediment thickness throughout the lake.  Once the mapping process was completed the POA was able to identify areas that needed dredging and how much material was there.  This allows for much better budgeting and accountability.

Results:  The POA was excited to have information based on real numbers (lake and sediment survey).  The hydrographic survey results are an essential part of the decision making process with regards to the sediment removal planning.  Now they have real information, which gives them a clear picture of what to do in the future.

Action Plan:   The POA has hired a professional dredging contractor to clean out specified problem areas identified during the hydrographic survey process.  The POA will be using the hydrographic survey information as a baseline for all future work and will adjust the map as dredging wraps up.  In the end the primary problem facing the POA was not simply the sediment in the lake but rather not knowing the facts about the lake to make the best decisions.  The POA now has the facts needed to create a comprehensive plan that will accurately represent the work being completed.  Plus members have a wonderful contour map to assist with fishing!

The Mapping Network surveyed the bottom of the lake including the sediment depths. This map shows the lake water depth as blue contours lines as well as a color shaded sediment thickness. This specialized technology allows the POA to easily locate problem areas.

The Mapping Network surveyed the bottom of the lake including the sediment depths. This map shows the lake water depth as blue contours lines as well as a color shaded sediment thickness. This specialized technology allows the POA to easily locate problem areas.

The Mapping Network is an industry leader in Hydrographic Surveys, Bathymetry, Geographic Information Systems Consulting, Data Conversion, and GPS Data Collection.  We specialize in terrain and sub-surface (bathymetry) GPS mapping.   If you are serious about maintaining  a high-quality golf course, lake or pond, be sure you have the ability to make the best decisions,  get your resource mapped by the professionals at The Mapping Network.   Give us a call or send an e-mail to find out more details.

phone:  (402) 241-8177

e-mail: info@themappingnetwork.com

website: www.themappingnetwork.com

Check out The Mapping Network on Facebook for more examples and success stories!

The Mapping Network is proud to announce their firm has been chosen by Cabela’s, the World’s Foremost Outfitter, as a Landowner Services provider for Cabela’s Trophy Properties throughout the United States.  Visit us on the Cabela’s Trophy Properties website >> click here

The Mapping Network:  www.TheMappingNetwork.com

A Nationwide Network of GPS Mapping Professionals

How does GPS Accuracy affect Lake Mapping Results?

When thinking about mapping a lake, it’s good to have a basic background of how the different methods of GPS can affect the quality of your data and ultimately the accuracy of your map.  Staff at The Mapping Network have been using GPS technology to map lakes since the 1990’s and we want to quickly cover some basics about the primary GPS collection methods available today.  It is important to understand how each type of GPS system will greatly influence the end result.  We are not going in depth on the theory and history of GPS but rather show simple examples of how accuracy on the initial data collection side is critical to creating an accurate map.

Diagram showing typical accuracy using standard hand held GPS (in blue), WAAS (yellow), Differential GPS (red). In this example one point was collected inside the red circle. Based on accuracy ratings for the standard GPS we would expect the point to be placed somewhere in the blue circle. If using WAAS it should land somewhere in the yellow circle and if using Differential GPS it should be near the red circle.

Brief Overview of GPS

Global positioning system (GPS) is a satellite navigation system developed in the early 1970s by the Department of Defense to overcome certain obstacles in navigation. Since then, the GPS navigation system has made its way to the public in the mid to late 1990s. Over the past decade, the accuracy of GPS has greatly increased in part from introducing new, more accurate satellites along with more sophisticated hardware and software for the ground units themselves. GPS computes its position based on time. This distance is computed based on the speed of light distance between the satellite and the receiver. The result is a z,y,z location on the earth. Typical hand held GPS units without extra enhancements can be anywhere from 10 to 30 meters with regards to locational horizontal accuracy.

Increased Forms of Accuracy with GPS

WAAS

Wide Area Augmentation System (WAAS) is a navigation system developed by the Federal Aviation Administration (FAA) to enhance the accuracy of GPS units onboard aircraft. WAAS uses ground based reference stations located around the Western Hemisphere to measure small variations in the GPS satellite messages. The typical horizontal accuracy of WAAS is within 3-7 meters to the user according to the FAA website.  The level of accuracy will be affected by the type of hardware and software being used to receive the signal. WAAS navigation system is only available in North America.

Differential GPS

Differential GPS helps fix errors with basic GPS mapping. This works by determining the inaccuracy from the GPS by comparing the locations of a stationary receiver location and a known location. Since the location of the DGPS is known, it’s able to send out a transmission to all DGPS equipped receivers near the area with the correct radio signal transmission. Using professional grade equipment this is typically accurate to 50 cm horizontal real-time and up to 10 cm by post processing.

RTK

Real Time Kinematic (RTK) system navigation is the most accurate option for mapping. RTK is capable of providing accuracies to within a centimeter both horizontally and vertically. RTK is mostly used for land surveying and land topography services because it is very accurate for capturing x,y,z (Lat, Long and Elevation).

How Does This Affect the Lake Map?

Creating contour maps starts with collecting data points throughout the lake.  These points then create a 3D model of the lake bottom where a number of different types of analyses can be performed.  In regard to locational accuracy, if we collect a single point on the lake, the point we are collecting will have a x, y (latitude and longitude provided by GPS).  If we are using a standard handheld unit that point is probably going to fall anywhere within a 15 meter radius.  Now let’s say we are using a WAAS enabled GPS system like what is found on the Lowrance HDS unit.  In this case we should expect the point to fall within a 3-4 meter radius of the actual location.  Look at the illustration above to better visualize what this means for accuracy.  If the water depth was 3.5 ft deep at the point collected you right away see where using a handheld unit or even a WAAS enabled unit can present all sorts of issues.  The 3.5 ft depth could be on land or still be in the water but 3 meters off.  The typical software used to process the data will then have to greatly generalize the contour map.  This type of mapping can be valuable for general recreation uses or quick management calculations but will be based off of a general estimate and would not be useful for information where accuracy is needed.

So how do we go about collecting accurate data?  According to the US Army Corps of Engineers specs the GPS location needs to be sub meter accurate.  This means using the correct Differential GPS or RTK system will achieve the locational accuracy required to generate an accurate map.

We understand there are different levels of needs for various clients and many times using a WAAS system will provide enough information to the client.  We call these recreational grade maps where general contours and depths can be seen and should be used as general reference maps.  These maps can look nice from a visual standpoint but provide little quantitative value.

Most projects require a certain level of accuracy that we call professional grade maps.  These maps can be used to generate accurate water volume, sedimentation rates, dredging or excavation planning and verification.

The Mapping Network provides the consumer with different accuracy levels based on the needs of the project.  It is very important to understand the different types of data collection because it is a critical component to a successful lake map.

As is with anything else in life, you get what you pay for!

——————————————–

The Mapping Network is an industry leader in Hydrographic Surveys, Bathymetry, Geographic Information Systems Consulting, Data Conversion, and GPS Data Collection.  We specialize in terrain and sub-surface (bathymetry) GPS mapping.   If you are serious about maintaining  a high-quality golf course, lake or pond, be sure you have the ability to make the best decisions,  get your resource mapped by the professionals at The Mapping Network.   Give us a call or send an e-mail to find out more details.

phone:  (402) 241-8177

e-mail: info@themappingnetwork.com

website: www.themappingnetwork.com

Check out The Mapping Network on Facebook for more examples and success stories!

The Mapping Network is proud to announce their firm has been chosen by Cabela’s, the World’s Foremost Outfitter, as a Landowner Services provider for Cabela’s Trophy Properties throughout the United States.  Visit us on the Cabela’s Trophy Properties website >> click here

The Mapping Network:  www.TheMappingNetwork.com

A Nationwide Network of GPS Mapping Professionals

Property Owner Association Uses Hydrographic & Sediment Surveys to Create Strategic Sediment Removal Plan

The Mapping Network Hydrographic Survey Team exceeds expectations for Property Owner Association.

Sediment problems are inevitable in all lakes and at some point removal is required.  Lake dredging and/or excavation can be an expensive process and requires accurate planning to be as cost-efficient as possible.   A lake Property Owners Association (POA) had been dealing directly with the challenges associated with sedimentation in their lake.  The POA decided they needed to quantify the sediment problem to create a sustainable sediment management plan.  The president of the board spearheaded an effort to get a hydrographic and sediment survey completed.  The president contacted several hydrographic survey companies and chose The Mapping Network to provide this service based on experience in the industry and listening to the needs of the POA.

Lake Survey Purpose:  The primary objective of the hydrographic and sediment survey was to better understand the condition of the lake by charting the existing lake contours along with mapping the sediment thickness throughout the lake.  Once the mapping process was completed the POA was able to identify areas that needed dredging and how much material was there.  This allows for much better budgeting and accountability.

Results:  The POA was excited to have information based on real numbers (lake and sediment survey).  The hydrographic survey results are an essential part of the decision making process with regards to the sediment removal planning.  Now they have real information, which gives them a clear picture of what to do in the future.

Action Plan:   The POA has hired a professional dredging contractor to clean out specified problem areas identified during the hydrographic survey process.  The POA will be using the hydrographic survey information as a baseline for all future work and will adjust the map as dredging wraps up.  In the end the primary problem facing the POA was not simply the sediment in the lake but rather not knowing the facts about the lake to make the best decisions.  The POA now has the facts needed to create a comprehensive plan that will accurately represent the work being completed.  Plus members have a wonderful contour map to assist with fishing!

The Mapping Network surveyed the bottom of the lake including the sediment depths. This map shows the lake water depth as blue contours lines as well as a color shaded sediment thickness. This specialized technology allows the POA to easily locate problem areas.

The Mapping Network surveyed the bottom of the lake including the sediment depths. This map shows the lake water depth as blue contours lines as well as a color shaded sediment thickness. This specialized technology allows the POA to easily locate problem areas.

The Mapping Network is an industry leader in Hydrographic Surveys, Bathymetry, Geographic Information Systems Consulting, Data Conversion, and GPS Data Collection.  We specialize in terrain and sub-surface (bathymetry) GPS mapping.   If you are serious about maintaining  a high-quality golf course, lake or pond, be sure you have the ability to make the best decisions,  get your resource mapped by the professionals at The Mapping Network.   Give us a call or send an e-mail to find out more details.

phone:  (402) 241-8177

e-mail: info@themappingnetwork.com

website: www.themappingnetwork.com

Check out The Mapping Network on Facebook for more examples and success stories!

The Mapping Network is proud to announce their firm has been chosen by Cabela’s, the World’s Foremost Outfitter, as a Landowner Services provider for Cabela’s Trophy Properties throughout the United States.  Visit us on the Cabela’s Trophy Properties website >> click here

The Mapping Network:  www.TheMappingNetwork.com

A Nationwide Network of GPS Mapping Professionals

Property Owner Association Uses Hydrographic & Sediment Surveys to Create Strategic Sediment Removal Plan – Resulting in Hundreds of Thousands in Savings

The Mapping Network Hydrographic Survey Team exceeds expectations for Property Owner Association.

Overview:  A lake property association (POA) has been dealing directly with the challenges associated with sedimentation in their lakes for over 20 years.  In 2002 The Board of Directors created a 30 year sediment removal and management plan (2002-2031).  They looked at 3 different options: A) hiring a dredging professional, B) leasing dredging equipment and use current POA staff to operate, or C) purchasing a new dredge and using POA staff to operate.  They contacted two environmental consultants for cost estimates over the 30 year process.  The estimates ranged from $1,000,000 to $5,000,000 which left the POA in a difficult position of trying to make a long term management decision based on wide ranging potential costs.  In the end the POA decided to purchase their own dredging equipment an utilize existing staff and volunteers to operated the equipment.

In House Accountability Challenges:  After nearly a decade of in house dredging the POA Board of Directors was unable to quantify and verify results.  When reviewing the budget requests from the lakes and dam committee, they realized they were spending a lot of resources without having clear information on how successful the sediment removal process had been over the years.

New Vision:  The POA decided they needed to quantify the sediment problem to create a sustainable sediment management plan.  The president of the board spearheaded an effort to get a hydrographic and sediment survey completed.  The president contacted several hydrographic survey companies and chose The Mapping Network to provide this service based on experience in the industry and listening to the needs of the POA.

Lake Survey Purpose:  The primary objective of the hydrographic and sediment survey was to better understand the condition of the lake by charting the existing lake contours along with mapping the sediment thickness throughout the lake.  Once the mapping process was completed the POA was able to identify areas that needed dredging and how much material was there.  This allows for much better budgeting and accountability.

Results: The POA was excited to have information based on real numbers (lake and sediment survey).  The hydrographic survey results are an essential part of the decision making process with regards to the sediment removal planning.  After 20 years of dredging and several studies performed by consultants they felt for the first time they finally understood the problem and how to manage it.  Now they have real information, which gives them a clear picture of what to do in the future.

Future: Members of the POA say they will completely change course by finishing up the current in house dredging work and then sell all dredging equipment.  They will then work with a  professional dredging contractor to clean out specified problem areas identified during the hydrographic survey process.  Understanding the true extent of the lake sediment distribution in the lake will save the POA an estimated $200,000 to $300,000 in costs by selling unnecessary equipment and strategic dredging planning.  The POA will be using the hydrographic survey information as a baseline for all future work and will adjust the map as dredging continues.

Conclusion:  In the end the primary problem facing the POA was not the sediment in the lake but rather not knowing the facts about the lake to make the best decisions.  The POA now has the facts needed to create a comprehensive plan that will accurately represent the work being completed.  Plus members have a wonderful contour map to assist with fishing!

The Mapping Network surveyed the bottom of the lake including the sediment depths. This map shows the lake water depth as blue contours lines as well as a color shaded sediment thickness. This specialized technology allows the POA to easily locate problem areas.

The Mapping Network surveyed the bottom of the lake including the sediment depths. This map shows the lake water depth as blue contours lines as well as a color shaded sediment thickness. This specialized technology allows the POA to easily locate problem areas.

The Mapping Network is an industry leader in Hydrographic Surveys, Bathymetry, Geographic Information Systems Consulting, Data Conversion, and GPS Data Collection.  We specialize in terrain and sub-surface (bathymetry) GPS mapping.   If you are serious about maintaining  a high-quality golf course, lake or pond, be sure you have the ability to make the best decisions,  get your resource mapped by the professionals at The Mapping Network.   Give us a call or send an e-mail to find out more details.

phone:  (402) 241-8177

e-mail: info@themappingnetwork.com

website: www.themappingnetwork.com

Check out The Mapping Network on Facebook for more examples and success stories!

The Mapping Network is proud to announce their firm has been chosen by Cabela’s, the World’s Foremost Outfitter, as a Landowner Services provider for Cabela’s Trophy Properties throughout the United States.  Visit us on the Cabela’s Trophy Properties website >> click here

The Mapping Network:  www.TheMappingNetwork.com

A Nationwide Network of GPS Mapping Professionals

How does GPS Accuracy affect Lake Mapping Results?

When thinking about mapping a lake, it’s good to have a basic background of how the different methods of GPS can affect the quality of your data and ultimately the accuracy of your map.  Staff at The Mapping Network have been using GPS technology to map lakes since the 1990’s and we want to quickly cover some basics about the primary GPS collection methods available today.  It is important to understand how each type of GPS system will greatly influence the end result.  We are not going in depth on the theory and history of GPS but rather show simple examples of how accuracy on the initial data collection side is critical to creating an accurate map.

Diagram showing typical accuracy using standard hand held GPS (in blue), WAAS (yellow), Differential GPS (red). In this example one point was collected inside the red circle. Based on accuracy ratings for the standard GPS we would expect the point to be placed somewhere in the blue circle. If using WAAS it should land somewhere in the yellow circle and if using Differential GPS it should be near the red circle.

Brief Overview of GPS

Global positioning system (GPS) is a satellite navigation system developed in the early 1970s by the Department of Defense to overcome certain obstacles in navigation. Since then, the GPS navigation system has made its way to the public in the mid to late 1990s. Over the past decade, the accuracy of GPS has greatly increased in part from introducing new, more accurate satellites along with more sophisticated hardware and software for the ground units themselves. GPS computes its position based on time. This distance is computed based on the speed of light distance between the satellite and the receiver. The result is a z,y,z location on the earth. Typical hand held GPS units without extra enhancements can be anywhere from 10 to 30 meters with regards to locational horizontal accuracy.

Increased Forms of Accuracy with GPS

WAAS

Wide Area Augmentation System (WAAS) is a navigation system developed by the Federal Aviation Administration (FAA) to enhance the accuracy of GPS units onboard aircraft. WAAS uses ground based reference stations located around the Western Hemisphere to measure small variations in the GPS satellite messages. The typical horizontal accuracy of WAAS is within 3-7 meters to the user according to the FAA website.  The level of accuracy will be affected by the type of hardware and software being used to receive the signal. WAAS navigation system is only available in North America.

Differential GPS

Differential GPS helps fix errors with basic GPS mapping. This works by determining the inaccuracy from the GPS by comparing the locations of a stationary receiver location and a known location. Since the location of the DGPS is known, it’s able to send out a transmission to all DGPS equipped receivers near the area with the correct radio signal transmission. Using professional grade equipment this is typically accurate to 50 cm horizontal real-time and up to 10 cm by post processing.

RTK

Real Time Kinematic (RTK) system navigation is the most accurate option for mapping. RTK is capable of providing accuracies to within a centimeter both horizontally and vertically. RTK is mostly used for land surveying and land topography services because it is very accurate for capturing x,y,z (Lat, Long and Elevation).

How Does This Affect the Lake Map?

Creating contour maps starts with collecting data points throughout the lake.  These points then create a 3D model of the lake bottom where a number of different types of analyses can be performed.  In regard to locational accuracy, if we collect a single point on the lake, the point we are collecting will have a x, y (latitude and longitude provided by GPS).  If we are using a standard handheld unit that point is probably going to fall anywhere within a 15 meter radius.  Now let’s say we are using a WAAS enabled GPS system like what is found on the Lowrance HDS unit.  In this case we should expect the point to fall within a 3-4 meter radius of the actual location.  Look at the illustration above to better visualize what this means for accuracy.  If the water depth was 3.5 ft deep at the point collected you right away see where using a handheld unit or even a WAAS enabled unit can present all sorts of issues.  The 3.5 ft depth could be on land or still be in the water but 3 meters off.  The typical software used to process the data will then have to greatly generalize the contour map.  This type of mapping can be valuable for general recreation uses or quick management calculations but will be based off of a general estimate and would not be useful for information where accuracy is needed.

So how do we go about collecting accurate data?  According to the US Army Corps of Engineers specs the GPS location needs to be sub meter accurate.  This means using the correct Differential GPS or RTK system will achieve the locational accuracy required to generate an accurate map.

We understand there are different levels of needs for various clients and many times using a WAAS system will provide enough information to the client.  We call these recreational grade maps where general contours and depths can be seen and should be used as general reference maps.  These maps can look nice from a visual standpoint but provide little quantitative value.

Most projects require a certain level of accuracy that we call professional grade maps.  These maps can be used to generate accurate water volume, sedimentation rates, dredging or excavation planning and verification.

The Mapping Network provides the consumer with different accuracy levels based on the needs of the project.  It is very important to understand the different types of data collection because it is a critical component to a successful lake map.

As is with anything else in life, you get what you pay for!

——————————————–

The Mapping Network is an industry leader in Hydrographic Surveys, Bathymetry, Geographic Information Systems Consulting, Data Conversion, and GPS Data Collection.  We specialize in terrain and sub-surface (bathymetry) GPS mapping.   If you are serious about maintaining  a high-quality golf course, lake or pond, be sure you have the ability to make the best decisions,  get your resource mapped by the professionals at The Mapping Network.   Give us a call or send an e-mail to find out more details.

phone:  (402) 241-8177

e-mail: info@themappingnetwork.com

website: www.themappingnetwork.com

Check out The Mapping Network on Facebook for more examples and success stories!

The Mapping Network is proud to announce their firm has been chosen by Cabela’s, the World’s Foremost Outfitter, as a Landowner Services provider for Cabela’s Trophy Properties throughout the United States.  Visit us on the Cabela’s Trophy Properties website >> click here

The Mapping Network:  www.TheMappingNetwork.com

A Nationwide Network of GPS Mapping Professionals

How does GPS Accuracy affect Lake Mapping Results?

When thinking about mapping a lake, it’s good to have a basic background of how the different methods of GPS can affect the quality of your data and ultimately the accuracy of your map.  Staff at The Mapping Network have been using GPS technology to map lakes since the 1990’s and we want to quickly cover some basics about the primary GPS collection methods available today.  It is important to understand how each type of GPS system will greatly influence the end result.  We are not going in depth on the theory and history of GPS but rather show simple examples of how accuracy on the initial data collection side is critical to creating an accurate map.

Diagram showing typical accuracy using standard hand held GPS (in blue), WAAS (yellow), Differential GPS (red). In this example one point was collected inside the red circle. Based on accuracy ratings for the standard GPS we would expect the point to be placed somewhere in the blue circle. If using WAAS it should land somewhere in the yellow circle and if using Differential GPS it should be near the red circle.

Brief Overview of GPS

Global positioning system (GPS) is a satellite navigation system developed in the early 1970s by the Department of Defense to overcome certain obstacles in navigation. Since then, the GPS navigation system has made its way to the public in the mid to late 1990s. Over the past decade, the accuracy of GPS has greatly increased in part from introducing new, more accurate satellites along with more sophisticated hardware and software for the ground units themselves. GPS computes its position based on time. This distance is computed based on the speed of light distance between the satellite and the receiver. The result is a z,y,z location on the earth. Typical hand held GPS units without extra enhancements can be anywhere from 10 to 30 meters with regards to locational horizontal accuracy.

Increased Forms of Accuracy with GPS

WAAS

Wide Area Augmentation System (WAAS) is a navigation system developed by the Federal Aviation Administration (FAA) to enhance the accuracy of GPS units onboard aircraft. WAAS uses ground based reference stations located around the Western Hemisphere to measure small variations in the GPS satellite messages. The typical horizontal accuracy of WAAS is within 3-7 meters to the user according to the FAA website.  The level of accuracy will be affected by the type of hardware and software being used to receive the signal. WAAS navigation system is only available in North America.

Differential GPS

Differential GPS helps fix errors with basic GPS mapping. This works by determining the inaccuracy from the GPS by comparing the locations of a stationary receiver location and a known location. Since the location of the DGPS is known, it’s able to send out a transmission to all DGPS equipped receivers near the area with the correct radio signal transmission. Using professional grade equipment this is typically accurate to 50 cm horizontal real-time and up to 10 cm by post processing.

RTK

Real Time Kinematic (RTK) system navigation is the most accurate option for mapping. RTK is capable of providing accuracies to within a centimeter both horizontally and vertically. RTK is mostly used for land surveying and land topography services because it is very accurate for capturing x,y,z (Lat, Long and Elevation).

How Does This Affect the Lake Map?

Creating contour maps starts with collecting data points throughout the lake.  These points then create a 3D model of the lake bottom where a number of different types of analyses can be performed.  In regard to locational accuracy, if we collect a single point on the lake, the point we are collecting will have a x, y (latitude and longitude provided by GPS).  If we are using a standard handheld unit that point is probably going to fall anywhere within a 15 meter radius.  Now let’s say we are using a WAAS enabled GPS system like what is found on the Lowrance HDS unit.  In this case we should expect the point to fall within a 3-4 meter radius of the actual location.  Look at the illustration above to better visualize what this means for accuracy.  If the water depth was 3.5 ft deep at the point collected you right away see where using a handheld unit or even a WAAS enabled unit can present all sorts of issues.  The 3.5 ft depth could be on land or still be in the water but 3 meters off.  The typical software used to process the data will then have to greatly generalize the contour map.  This type of mapping can be valuable for general recreation uses or quick management calculations but will be based off of a general estimate and would not be useful for information where accuracy is needed.

So how do we go about collecting accurate data?  According to the US Army Corps of Engineers specs the GPS location needs to be sub meter accurate.  This means using the correct Differential GPS or RTK system will achieve the locational accuracy required to generate an accurate map.

We understand there are different levels of needs for various clients and many times using a WAAS system will provide enough information to the client.  We call these recreational grade maps where general contours and depths can be seen and should be used as general reference maps.  These maps can look nice from a visual standpoint but provide little quantitative value.

Most projects require a certain level of accuracy that we call professional grade maps.  These maps can be used to generate accurate water volume, sedimentation rates, dredging or excavation planning and verification.

The Mapping Network provides the consumer with different accuracy levels based on the needs of the project.  It is very important to understand the different types of data collection because it is a critical component to a successful lake map.

As is with anything else in life, you get what you pay for!

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The Mapping Network is an industry leader in Hydrographic Surveys, Bathymetry, Geographic Information Systems Consulting, Data Conversion, and GPS Data Collection.  We specialize in terrain and sub-surface (bathymetry) GPS mapping.   If you are serious about maintaining  a high-quality golf course, lake or pond, be sure you have the ability to make the best decisions,  get your resource mapped by the professionals at The Mapping Network.   Give us a call or send an e-mail to find out more details.

phone:  (402) 241-8177

e-mail: info@themappingnetwork.com

website: www.themappingnetwork.com

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The Mapping Network is proud to announce their firm has been chosen by Cabela’s, the World’s Foremost Outfitter, as a Landowner Services provider for Cabela’s Trophy Properties throughout the United States.  Visit us on the Cabela’s Trophy Properties website >> click here

The Mapping Network:  www.TheMappingNetwork.com

A Nationwide Network of GPS Mapping Professionals