On the left hand side of the DSM map, the coloured scale shows metres in elevation. Metres above sea level but at what state of tide, high or low? In Guernsey where I live, we often have up to 10m vertical tidal movement.
Anybody know?
Hope this helps answer your question
sea level
noun
1.
the level of the surface of the sea with respect to the land, taken to be the
mean level between high and low tide, and used as a standard base for measuring heights and depths
thank Andrew. The level are a bit out around here then.
I believe the numbers on each map are based on where you took off from. There are some reasons for this and I can have our map/data guy explain a bit more if you still have more questions.
Yup, correct - the elevation values are based on your takeoff location (in meters), so a value of 0 will be an elevation equal to that of your takeoff point.
If you’re interested in generating really high accuracy elevation models or referencing the elevations relative to the mean sea level or some other datum, then we can incorporate ground control information to the models if you have that available - just let us know!
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Is it possible to edit/change the range of values for the DSM?
unfortunately not automatically without incorporating some ground control information to tie the elevations to actual MSL levels
Thanks Jeremy.
I have relatively flat land and noticed if a tree, grain bin, etc. is within map area it skews the DSM values so the land shows as one color.
Yup, that will happen; if you’re interested in getting ground elevation information we have some experimental layers available which remove the vegetation from the elevation map so you get a better representation of the ground level changes (essentially a Digital Terrain Model in addition to the Digital Surface Model you’re getting already). Let me know if you want me to activate these for your account and you can see how the next map turns out (or I can re-run your previous jobs to see how they come out).
Jeremy
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Please Jeremy, I would like to try this, as elevations so far have been out.I would find it hard to convince a surveyor to pay for my services with such inaccuracies. Surely we can work on this.
Hi markaguille,
Sorry for the slow response; I’ve enabled those features for your account, so the alternative layers will be generated (along with the layers you already get) for any maps you generate from now onwards). Are there any particular maps you have that contain a tree etc. throwing out the DSM scaling you’d like me to rerun with the new settings so you can compare the results?
Jeremy
Hi Jeremy,
Cold you rerun the Saint Sampson Marina map for me. I don’t think there is a tree in this map, what else may be causing it?
Thanks in advance,
Mark G.
Hello @jeremy,
I know this is an old thread, but i have been working with some local farmers and the DSM’s are way off on elevation. We are hoping to get something a lot more accurate if possible. We are also in talks with a seed company that want to use our services, but we need some pretty accurate data to present to them. Any help would be much appreciated.
Thanks
@jeremy Hi Jeremy, can you give us an update on the DTM layer as I think a few of us would like to improve our DSM outputs?
Are you taking into account that the elevations are going to be based on your takeoff location when checking the accuracy?
Yes, the elevations shown to the left are not even close. When taking into account the elevations are based off of my take off point they shouldnt be anywhere from 20-40’ difference in an open cornfield. Maybe a variance of a few feet, but not tens of feet. We have been testing Pix4D also and the elevations are pretty accurate. We can measure crop height too. Also, the camera malfunction at the end of mission checkpoints has been solved due to taking one pic in DJI Go and then loading your app. It seems that the app doesnt like a freshly formatted card. I saw that on a thread and tried it. Works every time now.
Please let me know if we are doing or reading something wrong. Thanks
Hi Roger,
I’ve enabled the DTM and contour permissions for your account, so any maps you make from now on will have those layers as well and you can compare to the DSM. If you’d like any of your existing maps reprocessed to add in the DTM layer then let me know which ones and I’ll restart them.
As always, feedback on the new layers very much appreciated!
Hi Tyler,
Had a quick look at a couple of your field maps and the elevations don’t look too extreme (elevation differences of about 2m across the field) - could you send me links (or map names, flight IDs, etc.) to the ones you’ve seen particular issues with and I can investigate?
N.b. the elevation values given in the colourbar on the left hand side of the data page are global values based on your takeoff location; there can be some inaccuracy in the absolute values, but if you look at the relative differences then they should be more reasonable. Happy to discuss more on a specific map / data set if you want to pm me.
We will be releasing more fine-grained control over the DSM colouring and scaling in the near future, so hopefully this will address the confusions with global and local values that sometimes crop up.
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