Topographic DTM maps

[R.Cowan]

I have a customer requesting a topographic map of a 40 acre site. I'm planning on capturing the data with my Mavic 3E. Survey grade accuracy is not needed. A couple of questions. Will RTK or GCP's be needed? Also looking for recommendations for a map processing provider with pay as you go option. Any input will be greatly appreciated.

 

[AMann]

There are many different products where you pay as you go to create orthophoto images and topographic maps. The logistics of the project are really important.

What type of land is it, are there a lot of hills, are there trees, or other discernible landmarks for image processing to be able to find matching points? If not, or if they’re very tall trees, you may need ground control points or RTK to help out. If you are going for any accuracy, these will help but I wouldn’t call it an orthophoto without using either of them because you can’t guarantee that the scale will be the same in any direction on the orthophoto and these errors will be compounded on the topographic map produced from them.

So if your customer wants you to use the images for producing a topographic map, I would certainly go with RTK and/or using numerous GCP’s.

 

[R.Cowan]

Thanks AMan for your input. I haven't seen the property yet, but it is 50 miles SW of Houston near a major river. Relatively flat land. It does have trees and vegetation. I will probably visit with my customer to determine if this is just a one time mission or if others will be needed. I need to justify the financial investment for RTK module and RTK network service in Texas which unfortunately isn't free.

 

[AMann]

RTK is also doable with using a base station you place on site - but as a less expensive way for doing this with my M2P’s, I purchased 2 SparkFun GPS units to survey in my GCP’s. You only really need 1 to do it if you have cellular service and can use your phone to receive the RTK correction information, but you need 2 if you are doing your own onsite RTK setup where one serves as the base station and the second as the rover that you use to plot in your GCP markers on the ground. The SparkFun units are survey grade but are surprisingly inexpensive and connect via Bluetooth to a phone as the interface. The ones I bought need external telemetry transmitters - also available from SparkFun to be able to work with each other as a base and rover setup. There are also free RTK services available if you have a regional government-sponsored CORS RTK site nearby. Some states sponsor it, but I don’t know about Texas.

SparkFun RTK Surveying Kit

The RTK Surveyor Kit has everything you need to get centimeter level global positioning measurements using GNSS RTK.

www.sparkfun.com

SiK Telemetry Radio V3 - 915MHz, 100mW

The 915MHz SiK Telemetry Radio V3 is a lightweight and inexpensive open source radio platform that can allow for ranges of 300m or more out of the box.

www.sparkfun.com

 

[mavictk]

Thanks AMan for your input. I haven't seen the property yet, but it is 50 miles SW of Houston near a major river. Relatively flat land. It does have trees and vegetation. I will probably visit with my customer to determine if this is just a one time mission or if others will be needed. I need to justify the financial investment for RTK module and RTK network service in Texas which unfortunately isn't free.

Have you reviewed the land with Google maps before driving out there?

 

[liam788fh]

RTK is also doable with using a base station you place on site - but as a less expensive way for doing this with my M2P’s, I purchased 2 SparkFun GPS units to survey in my GCP’s. You only really need 1 to do it if you have cellular service and can use your phone to receive the RTK correction information, but you need 2 if you are doing your own onsite RTK setup where one serves as the base station and the second as the rover that you use to plot in your GCP markers on the ground. The SparkFun units are survey grade but are surprisingly inexpensive and connect via Bluetooth to a phone as the interface. The ones I bought need external telemetry transmitters - also available from SparkFun to be able to work with each other as a base and rover setup. There are also free RTK services available if you have a regional government-sponsored CORS RTK site nearby. Some states sponsor it, but I don’t know about Texas.

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SiK Telemetry Radio V3 - 915MHz, 100mW

The 915MHz SiK Telemetry Radio V3 is a lightweight and inexpensive open source radio platform that can allow for ranges of 300m or more out of the box.

www.sparkfun.com

Great