Hi Folks,
New to the forum, hope this would be an appropriate category.
I have been diving into researching how I can make contour maps of farms, anything from 10 to several hundred Hectares. Having good quality aerials is vital too. I imagine a plane is most suited to this, and I am looking for autonomous flight as far as possible.
I'm not having much luck finding out what would be the best way to achieve this- or whether it is possible on the cheaper end of things. I have had difficulty finding reference to this application regarding UAVs.
Can anyone point out any key considerations & recommendations for the hardware side of things, as well as any software ideas.
Does anyone else work with creating topographic maps?
Many thanks for any input
Richard
Replies
Hi Richard,
Im still a newbie in building UAVs/ Drones but what i know about contour is you need to have a Digital Terrain Model (DTM) first. Then you can use software like global mapper to do it for you. Only need to select what interval you need and run it. Hope this helps :-D
Hi Fouad,
We never used a Z correction so the accuracy I referred too was on XY. Cheers,
Morgan
its vwry important to remid that to get accuracies on the sub meter order the ground control points must be taken or set with a gnss rtk system. not with a handgeld gps system alone like the garmin etrex series.
also with the onboard gps camera the orthomosaic accuracy wil be 2.5 meters at best
I think I can help out here. Done this quite a bit...
Sounds like you have the aircraft side of things pretty much licked. I just got my E382 back and should have it in the air this weekend for some test flights. The other posts concerning Canon cameras and CHDK are spot-on. The Canon stuff automatically writes your coordinates into the EXIF header of each image. Even on LARGE setting, a decent memory card can hold nearly 6500 images...more than enough for a single flight. While I haven't tried this yet, the Canon cameras allow you to log GPS data that you could probably use as ground control points for later input into your post-processing software.
Post-processing of your imagery...
This is a fairly broad subject and how you go about it depends on a variety of factors. Personally, I use Photoscan because it produces IMO top-notch mosaics of the imagery and simultaneously produces a point cloud and a DEM. It ain't cheap by any means, but its results are worth their weight in gold, again IMO.
To produce contours, you will need something that can read the elevation in the DEM and create vector features, lines or closed polygons. High-end stuff like ArcGIS with Spatial Analyst or 3D Analyst can do this, but Global Mapper is much better suited for handling 3D data. I have used both and Global Mapper has ArcGIS beat hands-down with regards to raw data processing...and it is about 10% of the cost of ArcGIS. Now, for "pretty" maps...or presentation quality maps...Global Mapper just doesn't have that stuff built into its framwork...yet. ArcGIS is the way to go here, but plan on dropping $3500-4000 for a basic single-seat license. Eventually, it will pay for itself, but the pay-out timeframe is a direct function of how much business you have and how long you are willing to stay in the red.
Global Mapper also allows you to do what we refer to as a "drape" using loaded elevation (DEM) data and the associated aerial imagery mosaic. ArcGIS can do this as well, but you have to have a license to the 3D Analyst extension...cough up another $3000 please. The "drape" loads and stretches the imagery mosaic over the DEM and produces a 3D rendering of the scene that can be manipulated in 3D virtual space.
Other things that GM allows you to do cheaply are terrain analysis tasks such as volumetric calculations. These are very useful for cut-and-fill or material removal calculations. You can also use them to estimate the volume of a feature on the ground such as a wood pile or a earthen mound.
My opinion...use Global Mapper for the 3D analysis. Export the vectors to an ESRI shapefile and then use ArcGIS (if you can afford it) to make the pretty map with all of the cartographic symbology and color ramps for your contour features.
This is only a small discussion of how to do this. To REALLY understand it, you need to get into the principles of analytic photogrammetry. There is a lot more to this than just taking pictures and welding them together. A good understanding of the subject can help you plan your flights and thereby produce considerably better imagery products.
Watch out for the FAA! They aren't civilian-drone friendly!!!
Hope this helped!!!
Hi Richard,
I've just built my second UAV so can give you some pointers. I'm still learning the more technical programming side of the APM but I have been getting great maps so hopefully I don't steer you in the wrong direction with my advice.
Yep - you need a plane because a multicopter just doesn't have the battery life you'll be needing. I strongly suggest a skywalker FPV style plane (just google it to see what it looks like). They are stable, easy to repair, can carry all the gear you'll be needing and are cheap. You'll need to get a 7 channel or more radio and reciever. I have a Turnigy 9x which was really cheap of hobbyking.com and hasn't given me any drama's as of yet. There's plenty of youtube videos explaining how to program them too.
You'll also need the APM 2.5 with the power module and GPS and telemetry gear. You'll also need a 10 to 12 megapixle camera with GPS built in and if you can get a canon model it just makes the photo capture much easier (explain why in a min).
You need a computer, preferably a laptop so you can take it into the field. You will load the Mission planner software (Google it) onto it and that will let you plan your flights and upload waypoints to the APM.
I'm assuming your good to get all this gear and build your plane - possibly the only thing to mention when building your plane is to try keep all the aerials (radio receiver, telemetry, GPS and Camera) as far apart as reasonably possibly because all the radio information can override one of your other signals and that can lead to crashes.
Ok once ya plane is built, cut a hole in the bottom of the fuselage for the camera to point down to the ground. I suggest using a bit of foam to absorb any vibrations. The reason for getting a canon is because you can load software to canon cameras called CDHK (google it). You need to load an intervolometer script (Google it) which takes photos at predetermined frequency. DroneMapper (Google them) have a good script that I use. They are also who I use for my post processing.Well by the time you get to this stage you are ready to fly and will have read as much info as me and spent somewhere around a thousand bucks.
Getting your contours can be achieved through post-processing using DroneMapper. Jon-Pierre is the main contact, he has been awesome to deal with and I'm sure will see you right.
A quicker process may be to talk to the guys at Event38.com as they sell off the shelve ready made versions of what I've just told you about.
Good luck - keep us updated.
Morgan