Messages

1

General / Re: Gaps in exported DEM

« on: January 20, 2012, 07:37:53 PM »

There are no negative values in the GCPs and the DEM I produced is okay apart from the gaps.

Thanks.

2

General / Re: Gaps in exported DEM

« on: January 20, 2012, 06:58:07 PM »

I have run the model again, this time with the correct GCPs (X,Y and Z values). The resulting DEM looks the same as my original one - with the same gaps! This time the elevation values are realistic so it seems to be doing everything right, except cropping some parts of the final output. Any ideas?

Thanks.

3

General / Re: Gaps in exported DEM

« on: January 17, 2012, 01:49:02 PM »

Thank you - I see what I have done wrong now. Classic case of operator error!

I don't have the XY co-ordinates for my GCPs, only the elevation data. I input 4 GCPs based on graticules from a printed map, and assigned only X and Y values (I don't know the elevation of these parts). I was therefore telling Photoscan to produce a model based on 4 points with an elevation of 0 (ignoring all the GCPs with elevation but no XY values), which is why there were some negative values. This may also be why there were some gaps initially - if they were too far out perhaps they could not be represented in a DEM.

I have got around this by using the 4 XY GCPs to estimate the X and Y co-ordinates of the elevation GCPs, whilst retaining the original elevation details. I am now running the model based on the estimated XY values and the known elevation values (and not the 4 XY GCPs). I think this will work.

4

General / Re: Gaps in exported DEM

« on: January 16, 2012, 06:34:24 PM »

Thanks for the reply, the area with no data in the DEM is covered by plenty of points and I don't think there are enough gaps to stop it from calculating the height. The model in Photoscan also seems to have reconstructed the height in this area quite accurately, it is just on the DEM export that the problem occurs.

5

General / Gaps in exported DEM

« on: January 16, 2012, 02:49:07 PM »

Hello,

I am attempting to export a DEM created from 36 aerial photographs. The 3D model in photoscan looks very good and the DEM looks mostly good when viewed in ArcMap and ArcScene. The problem is that part of the area in the model didn't output in the DEM and I'm not sure why. There are some areas of water which have caused disturbance but these have been filled - there is a large section which looks fine in Photoscan and is not water, but has not exported in the DEM.

Any help would be much appreciated!

Thanks,

Rob