Topographic survey for residential question...

[Dan2112]

I am going to do some substantial landscaping and I would like to have a topological map of my property before I start. It's not large from a drone/job site perspective - it's only 6000 sq feet lot with a house in the center. The property is on a hill and has a sloping grade down from north to south and east to west with the north east corner being the highest spot.

I would like to generate a 1 ft topological map. Would a drone survey be able to achieve this accuracy? I can't imaging this would take a long time to complete. There are some trees on the property but the majority of the lot is weeds and old landscaping (railroad ties, wood stairs, etc).

My alternative is to stake out a grid out myself and do the rise/run measurements.

Dan

 

[jaja6009]

It would be easy to do. But, keep in mind what elevations would you be relating your elevations to? Do you have a vertical datum already in mind to compare your map to? I have run into this problem when using the various drone mapping software. If you let the software choose a default vertical datum it tends to not match what people are referring to.

Example: You know that an elevation point nearby is 28 ft above Mean Sea Level. You do not realize that this 28 ft above MSL is from using NAVD88 with Geoid 18 applied. You use your trusty Phantom 4 Pro to run this quick easy map mission and Pix4D then gives you a map that uses EGM 96 (Default in Pix4D) to give you ft above MSL that will be different than Geoid 18. EGM96 is not wrong, its just an older world gravity model that works great when you know that you must compare it to other maps in EGM 96. Disregard though if you just want to see the elevation change for this property only to visualize the slope. Just keep in mind that confusion could set in if there is something nearby that used a different vertical datum/geoid as their elevations will be shifted and different than yours.


To answer your questions, it would be very easy for a drone to do this. You could easily achieve centimeter accuracy by someone with real GNSS equipment and access to any of the various software. You could end up with any of the various GIS outputs like an orthmap (Google Map type view), contour map, shaded DEM (Digital Elevation Model), 3D point cloud. Just remember to compare apples to apples when comparing your new map to other maps or other known elevation points in your area.

 

[Gagey52]

GCPs take longer to sort than actually flying the mission. Today I set out 6 GCPs which took 1.5 hours to fly a 17 min mission.
Regards

 

[kshaw]

You can do a similar map with Google Earth and a KML file which delineates the boundary of your property. The KML file just overlays the map. This is not a topo, though. Google Earth also supports designating points on the map with pop up pictures. I work with a conservation group that maintains wood duck nesting boxes. We located all the boxes on the map and attached popup photos of each one. There should be some Youtupe videos on how to make KML files and load them onto the map.

 

[Enorda]

I read this as you are looking for locally referenced topo map. Since you are looking for a locally referenced, you don't need GCPs, and you really don't need to worry about the datums, etc. It isn't that you are looking for exact correct altitudes over MSL and you aren't looking for exact real world placement like a survey would provide, you just want to know how water will flow, where to put trees, maybe where to put a swale or berm. In that, it is really easy to do. Getting the contours of the property, and the different heights, you would have a cross hatched 3d map with perimeter, and I could add in low height altitude images around all trees. The GNSS solutions mentioned above for centimeter accuracy I don't think would be necessary since that would be centimeter accuracy for real world positioning, and as you said this is more for landscaping which isn't as critical for centimeter accuracy. Also paying for GNSS and RTK would put it cheaper to just hire a surveyor to do it all.

Personally I'd probably use DroneDeploy for flight automation, and Pix4d or WebODM to produce the map. At 1 ft intervals, that might take a while to produce, I think standard is 10', but it's just processing time and PC memory.