kopia lustrzana https://github.com/OpenDroneMap/docs
86 wiersze
4.2 KiB
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86 wiersze
4.2 KiB
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#####################
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Ground Control Points
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#####################
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Ground control points are useful for correcting distortions in the data and referencing the data to know coordinate systems.
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The format of the GCP file is simple.
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* The first line should contain the name of the projection used for the geo coordinates. This can be specified either as a PROJ string (e.g. ``+proj=utm +zone=10 +ellps=WGS84 +datum=WGS84 +units=m +no_defs``), EPSG code (e.g. ``EPSG:4326``) or as a ``WGS84 UTM <zone>[N|S]`` value (eg. ``WGS84 UTM 16N``)
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* Subsequent lines are the X, Y & Z coordinates, your associated pixels, the image filename and optional extra fields, separated by tabs or spaces:
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* Elevation values can be set to "NaN" to indicate no value
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* The 7th column (optional) typically contains the label of the GCP.
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GCP file format::
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<projection>
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geo_x geo_y geo_z im_x im_y image_name [gcp_name] [extra1] [extra2]
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...
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Example::
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+proj=utm +zone=10 +ellps=WGS84 +datum=WGS84 +units=m +no_defs
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544256.7 5320919.9 5 3044 2622 IMG_0525.jpg
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544157.7 5320899.2 5 4193 1552 IMG_0585.jpg
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544033.4 5320876.0 5 1606 2763 IMG_0690.jpg
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If you supply a GCP file called ``gcp_list.txt`` then ODM will automatically detect it. If it has another name you can specify using ``--gcp <path>``. If you have a gcp file and want to do georeferencing with exif instead, then you can specify ``--use-exif``. If you have high precision GPS measurements in your images (RTK) and want to use that information along with a gcp file, you can specify ``--force-gps``.
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`This post has some information about placing Ground Control Targets before a flight <http://diydrones.com/profiles/blogs/ground-control-points-gcps-for-aerial-photography>`_, but if you already have images, you can find your own points in the images post facto. It's important that you find high-contrast objects that are found in **at least** 3 photos, and that you find a minimum of 5 objects.
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Sharp corners are good picks for GCPs. You should also place/find the GCPs evenly around your survey area.
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The ``gcp_list.txt`` file must be created in the base of your project folder.
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For good results your file should have a minimum of 15 lines after the header (5 points with 3 images to each point).
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***************
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User Interfaces
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***************
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You can use one of two user interfaces for creating GCP files:
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* `POSM GCPi <https://github.com/posm/posm-gcpi>`_
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* `GCP Editor Pro <https://github.com/uav4geo/GCPEditorPro>`_
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---------
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POSM GCPi
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---------
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The POSM GCPi is loaded by default on WebODM. An example is available at `the WebODM Demo <http://demo.webodm.org/plugins/posm-gcpi/>`_. To use this with known ground control XYZ values, one would do the following:
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Create a GCP list that only includes gcp name (this is the label that will be seen in the GCP interface), x, y, and z, with a header with a proj4 string of your GCPs (make sure they are in a planar coordinate system, such as UTM. It should look something like this:
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::
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+proj=utm +zone=37 +south +ellps=WGS84 +datum=WGS84 +units=m +no_defs
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gcp01 529356.250827686 9251137.5643209 8.465
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gcp02 530203.125367657 9250140.80991621 15.781
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gcp03 530292.136003818 9250745.02372435 11.977
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gcp04 530203.125367657 9250140.80991621 15.781
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gcp05 530292.136003818 9250745.02372435 11.977
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Then one can load this GCP list into the interface, load the images, and place each of the GCPs in the image.
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--------------
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GCP Editor Pro
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--------------
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This app needs to be installed separately or can be loaded as a WebODM plugin from `https://github.com/uav4geo/GCPEditorPro <https://github.com/uav4geo/GCPEditorPro>`_
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Create a CSV file that includes the gcp name, northing, easting and elevation.
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::
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GCP Label,Northing,Easting,Elevation
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gcp01,529356.250827686,9251137.5643209,8.465
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gcp02,530203.125367657,9250140.80991621,15.781
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...
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Then import the CSV from the main screen and type ``+proj=utm +zone=37 +south +ellps=WGS84 +datum=WGS84 +units=m +no_defs`` in the ``EPSG/PROJ`` box.
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The following screen will display a map from where to select the GCPs to tag and import the respective images.
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`Help edit these docs! <https://github.com/OpenDroneMap/docs/blob/publish/source/tutorials.rst>`_
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