Pix4D Fields to QGIS workflow to ensure units are appropriate

Agriculture
1

Hi all,

I am exporting the Surface Model from Pix4DFields into QGIS for conversion to topography contours. I really don’t know much about QGIS except where to find the layer and raster tools. I need to ensure I am using the proper units….

  1. Does ‘Fields export the orthomosaic in the units I have it configured for?

  2. Does QGIS default to import as metric?

  3. How do I set both sides up so I can control the units?

I suspect QGIS is operating in non-descriptive drawing decimal units - maybe 1” or 1cm increments?

-Mike

2

Hi Mike,

PIX4Dfields will export the DSM in meters, which is normally the ellipsoidal height, and QGIS will also display it in meters.

3

Hmmm… I am getting far too many topo lines, as though it was in meters but the lines are showing up at inch increments. I’ll have to confirm my QGIS settings.
Are there any settings in ‘Fields I should check?

-Mike

4

If you are using imperial, it should be Feet. I assume there’s something wrong your QGIS settings yes..

5

Hmmmm… QGIS is all new to me.

The measurement settings are:

Ellipsoid - WGS 84 (EPSG:7030) ←Is this the issue?

Measurement units in Meters / square meters

I have the Coordinate and Bearing System set to

Map units (meters)and the Coordinate CRS set to EPSG:32615 - WGS 84 / UTM Zone 15N

I assume this matches the Surface Model Export??

-Mike

6

Jose,

I just checked my Pix4DFields set up and I see that Settings / Units are set to IMPERIAL.

Does that carry over to exports?

Further, I don’t see anywhere that controls the number system for vertical values… There is no mention of a vertical CRS, etc. Is it outputting ellipsoid or sea level #’s, and in what number system?

Your suggestions?

7

okaaay… After diving much further into the rabbit hole than I thought I would need to, what I have discovered is that exporting the ‘Fields surface model may not produce a file in the format expected by QGIS. I was using Band 1 which I assumed to be the Red channel, as the channel for QGIS to use in generating topos. Obvious, in hindsight, is that the channel is scaled to be between 0 and 255. So, yea that makes sense. Also, in hindsight, is that the values of this channel are scaled so that 0-255 map between the min / max elevations ‘Fields has computed during processing.

It is clear ‘Fields has all of the information. Is there a way to export the true elevations for each pixel? Note: I desire more horizontal resolution that what is provided in the “Water Management” export.

-Mike