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16 votes
Accepted

Drone aerial imagery to QGIS

Yes you need to Georeference the images. The Exif data explains where the photo was taken, so it describes where your drone/camera was at that time and often many other values (heigth, bearing etc). ...
Andrew Jeffrey's user avatar
7 votes

Drone aerial imagery to QGIS

Give RAPID for DJI a try. It will geo-reference and process up to 100 images from any DJI sensor or drone for free. The results are WGS84 Lat/Lon GeoTIFF format digital elevation models, point clouds ...
dronemapper's user avatar
5 votes

gdal_merge.py with memory constraints

gdal_merge allocates memory for whole raster at once so it runs quickly for datasets that fit into memory. If it is not you case, use gdalwarp tool which does tiling so you can control how much memory ...
o_7O's user avatar
  • 426
5 votes

How many forest clear cuts and how big are they?

Assuming you have attributes for the polygons for each type (clear cuts, young forest, etc), you can run the Dissolve tool in ArcGIS with this ‘Type’ column as the Dissolve_Field. This will aggregate ...
Rex's user avatar
  • 596
5 votes
Accepted

Georeference single drone image from EXIF data

As requested, posting my own (partial) answer. The actual math is not too bad, but there are surrounding issues making application difficult: UAV camera focal length specs seem to be before sensor ...
Houska's user avatar
  • 8,196
4 votes
Accepted

Georeferencing an oblique angle photograph in repeat-photograph studies

I've finally found a tool that does this. This task is referred to as mono-photogrammetry or monoplotting and involves referencing a single oblique and unrectified photo to a DEM to produce ...
Matt SM's user avatar
  • 1,851
3 votes
Accepted

What is the difference between Key-Point, Tie-Point in Photogrammetry?

I found this page in the Pix4D documentation which states: Keypoints are points of interest (high contrast, interesting texture) on the images that can be easily recognized. The number of keypoints ...
Fezter's user avatar
  • 21.9k
3 votes
Accepted

Getting a flat surface from DSM for height calculation?

Using the Trend tool does not work because it will only smooth the DSM surface, while what it is necessary is a DEM (bare-earth surface). What you want is a Canopy Height Model (CHM) (sometimes known ...
Andre Silva's user avatar
  • 10.3k
3 votes
Accepted

Photo has bright and darker on an aerial photo question

This is close to something known as Radiometric equalization. It is normally possible using professional softwares to parametrize and correct this in a semi-automatic way. But you can also do it ...
swiss_knight's user avatar
  • 10.5k
3 votes

Georeferencing single drone image from metadata (gimbal angles, flight angles)

An application like EXIFTool will allow you to see the pitch, roll, and yawl for both the camera and the aircraft. There are also Python solutions for reading the EXIF data from the aircraft camera ...
GBG's user avatar
  • 10k
3 votes

Measure an angle on an orthophoto or on a dense cloud

You can use field calculator to calculate the angle using this formula, where b is the horizontal length from one green cross to the next and a is the hight difference (vertical distance, the dotted ...
Babel's user avatar
  • 73.2k
3 votes

Can PPK (NOT RTK) be done with any mapping drone?

Post-processing depends on raw GNSS data being captured (pseudo-ranges for Code post-processing, Phase information for Carrier post-processing.) If the drone has only captured coordinates, you don't ...
Trams's user avatar
  • 749
2 votes

Drone aerial imagery to QGIS

You will probably have to georeference them! The metadata you're describing is really useful to let you know where the photo was taken, and it's usually a good first step that helps you understand ...
SaultDon's user avatar
  • 10.4k
2 votes

How many forest clear cuts and how big are they?

In QGIS, the Dissolve tool (in the tob bar, Vector > Geoprocessing Tools > Dissolve) is used to join adjacent polygons.
user106354's user avatar
2 votes

How many forest clear cuts and how big are they?

This seems better suited for a raster data type. Convert each polygon dataset into a raster where, clear-cut is coded as 1 and everything else 0. Then, just sum your rasters. The specified ...
Jeffrey Evans's user avatar
2 votes

Aerial Triangulation by using GPS height

In the context of structure-from-motion (SFM) photogrammetry - using ellipsoid heights for aerial triangulation is preferred because the ellipsoid is a mathematical model and this makes computations ...
Ralph Tee's user avatar
  • 1,732
2 votes
Accepted

PDAL error: "Couldn't create filter stage of type 'filters.cpd'"

This is cross-posted at the PDAL GitHub issue tracker. If you take a look at this table in the downloads section of the PDAL documentation, you will see that CPD is unfortunately not supported in the ...
chambbj's user avatar
  • 108
2 votes

Drone aerial imagery to QGIS

You may try this plugin Vertical Photo Placer github. It can read the GPS and other camera's metadata to perform simple geo-referencing for vertical drone photos.
mdc's user avatar
  • 156
2 votes

CHM (Canopy height model) = DSM (Digital surface model) - DTM (Digital terrain model)

Your idea is correct, however you might incur into some practical issues. The first is that the DTM and the stereos you are using seem to have a different height reference system. For example, as you ...
RafDouglas C. Tommasi's user avatar
2 votes

Where is the option to correct for rolling shutter in ESRI's Drone2Map software?

I have only seen references to a check-box in v1.3 documentation, but it wasn't there in the v1.3 instance I had access to. It appeared to be in the attribute table for the photos.
Dale Bridgford's user avatar
2 votes
Accepted

Options for making a DEM of single-return point cloud?

I am not as familiar with LasTools but you can try using a variety of tools in WhiteboxTools (https://www.whiteboxgeo.com/). Even though they mention "LiDAR" in the toolname/user manual, it ...
afrancio's user avatar
  • 146
2 votes

Does LiDAR tend to georeference better than photogrammetry?

No, the technical differences between Lidar or photogrammetrically-sourced point clouds have no influence on the final accuracy of datasets. Either can be off or "perfect" depending on the ...
bugmenot123's user avatar
  • 10.9k
2 votes

Couldn't find coordinate system NRW Netz zone 2 in Metashape

This is not a complete answer. I found a version of the definition at geotrafo e.U. The downloaded file for Netz77-NRW GK2.gtp looks like this: geotrafo_parameter_v46 Netz77-NRW_GK2 -566.1 -116.3 -390....
mkennedy's user avatar
  • 19k
1 vote

Focal length vs Principal point

I think you are getting wrong altitude values not because the focal distance. The altitudes computations depends of some factors: Numbers of photos for intersection calculus: If you have few photos ...
Natalia's user avatar
  • 11
1 vote

Interpolation of holes resulting from DTM groundfiltering of SfM pointcloud

Try the result if you use in SAGA: Grid-Tools-Close Gaps. But first, you need to bring pointcloud to the grid. To do this use Shapes-Point Clouds- Point Cloud to Grid.
Jost Hobic's user avatar
1 vote

Building height calculation from stereo Satellite images (Satellite Azimuth and Satellite Elevation)

If you know the date the image was taken, you can do the calculation based on the length of any objects shadow. h = sin(vertical angle of sun)*length shadow/cos(vertical angle of sun) The vertical ...
Erik's user avatar
  • 16.5k
1 vote
Accepted

DSM quality lower in ArcGIS Pro than PhotoScan

Making a slight alteration to the photogrammetry workflow will fix this issue. Running the component steps of the ArcGIS Pro Orthomapping DEM Wizard as separate geoprocessing steps solves both the ...
lambertj's user avatar
  • 3,057
1 vote
Accepted

Photogrammetry route flown using Litchi misses photos at some waypoints

DJI representatives have acknowledged that the problem with missed photos during waypoint missions is attributable to DJI firmware issues (see forum posts below). It's a known bug that should be ...
lambertj's user avatar
  • 3,057
1 vote
Accepted

Which type of point cloud is more accurate: from airborne LiDAR or aerial photos?

In my work, earthworks volume calculations and land-form shaping, I have found point clouds from Aerial photos more accurate than truck/tripod mounted laser scanning. I have to say we contract out the ...
ZrSiO4's user avatar
  • 904
1 vote

Dependence of point cloud data on camera parameters?

I believe you can't assume that. First of all (and correct me if I misunderstood) you are assuming that 3D points are spaced equally throughout your Point Cloud? That is actually a bad assumption ...
NAmorim's user avatar
  • 111

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