I generated imagery from a low flying drone (40 M AGL) equipped with a mica sense RedEdge multi-spectral camera and have processed the imagery in PIX4D and now am attempting to do some analysis in QGIS.

I am working to create CHM for several research plots and am noticing that the minimum height in DTMs generated from imagery on the same plot differ by about up to 2 meters. This is a big difference and will drastically skew results. Some of the plant heights are below 2 meters.

Any idea on how to generate a highly accurate DTM that can be used in CHM analysis?

I do have imagery from winter months and have considered generating a DTM from the leafless season but wonder about differences in ground level due to frost heaving and changes due to erosion. Any one have experience with canopy height modelling?

  • Generating a DTM from the winter image seems like a good start. Do you have any reliable control points in the plot (IE, points where you wouldn't expect the height to change much, such as buildings)?
    – csk
    Jun 7 '19 at 18:17
  • There are are some buildings within reasonable flight distance and there is also a road near by. Jun 7 '19 at 19:20
  • Did you use any ground control when collecting and processing your imagery? The accuracy of your DTM/DSM and any resulting analysis will wholly depend on this.
    – Dùn Caan
    Jun 9 '19 at 23:35
  • No I have not been able to use ground control points. Jun 27 '19 at 12:52

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