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  • Home
  • Welcome to Alteia keyboard_arrow_right
    Key Concepts keyboard_arrow_right
    What is Alteia What is Ground Sampling Distance GSD How is Accuracy defined in mapping drone Dataset Definition
    Getting Started keyboard_arrow_right
    Quick Guide to the Alteia Interface Ground Control Points GCP Best Practices Coordinate Reference Systems Local Coordinates Recommendation while creating a high precision project User Roles and Permissions Terms of Use of Alteia Viewing Approved Term of Use
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    2021 Changelog 2019-2020 Changelog
  • The Alteia Platform keyboard_arrow_right
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    Build
    Deploy
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    Agriculture and Forestry
    Mining and Aggregates
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    3D Reconstruction of Assets and Buildings BIM Use Case Examples CAD Files Support Import French Cadastre
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    Power and Utilities
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Local Coordinates

Alteia has the possibilities to have a Local Coordinates system.

Local Coordinates is a coordinates system that which are localized to minimize visual distortion / simplify measurement in a small region. It is specially good to make measurement and designed to be adapted for a particular region.

Please consult the CRS article if needed.

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Alteia Local coordinates is based on a transformation with the help of GCPs from WGS84 Datum to the desired local coordinates. 

Consequently those Ground Control Point has to be measured with the wished local coordinates and also in WGS84 (long, lag) DATUM.

1. Workflow

Local coordinates can be specified during the site creation.

Step 1: Click on create a Site

Step 2: In the Site properties, please choose the global site CRS.

Step 3: After choosing your global site CRS please click on Define Local CRS

There are three ways to define the Local CRS:

  • Single local-global coordinates file (.csv)
  • Separate local and global coordinates files (.csv)
  • JXL file
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IMPORTANT

  • The global coordinates, mentioned here, does not correspond to the GLOBAL SITE CRS. It correspond to the reference for the transformation. And it must be in WGS84 (EPSG:4326). The GLOBAL SITE CRS refers to the system you are using on the platform.
  • DO NOT forget to choose the unit in which the local coordinate is written

You can find below example files :

coordinates.jxl

Single Local global Control point.csv

Local Control point.csv

Global Control point .csv

1.1 Single local-global coordinates csv file

It allows the user to embed on a same CSV file, for a given point on the earth the correlation between a global system and a local system.

This CSV file must respect the following rules :

  • No Header
  • Must contain at least 3 points
  • Supported separator must be ,
  • Global coordinates of the GCP must be in WGS84 (EPSG:4326)
  • Must have the following structure as shown in the example table below (The column must have the same order (first local coordinates followed by the WGS84 coordinates)) :
    GCP ID Northing or Y axes (local units) Easting or X axes (local units) Elevation (local units) Latitude (deg) Longitude (deg) Ellipsoid Height (m)
    gcp 0 9951.901 11728.371 788.614 34.71285 -118.13166

    677.058928

    gcp 1 9864.197 11796.451 790.885 34.71261 -118.13143  679.331512
    gcp 2 9793.678 11671.38 787.715 34.71242 -118.13185

    676.168511

    gcp 3 9887.278 11570.888  788.415 34.71267 -118.13218 

    676.866717

1.2 Separate local and global coordinates files (.csv)

  • No Header
  • Must contain at least 3 points
  • Supported separator must be ,
  • Global coordinates of the GCP must be in WGS84 (EPSG:4326)
  • Must have the following structure as shown in the example table below (The column must have the same order (first local coordinates

    followed by the WGS84 coordinates)) :
    GCP Global CRS csv :

    GCP ID Longitude (deg) Latitude (deg) Ellipsoid Height (m)
    gcp 0 -118.13166 34.71285 677.058928
    gcp 1 -118.13143 34.71261 679.331512
    gcp 2 -118.13185 34.71242 676.168511
    gcp 3 -118.13218 34.71267 676.866717
    GCP Local CRS csv :
    GCP ID Easting or X axes (local units)

    Northing or Y axes (local units)

    Elevation (local units)
    gcp 0 11728.371  9951.901 788.614
    gcp 1 11796.451 9864.197 790.885
    gcp 2 11671.38 9793.678 787.715
    gcp 3 11570.888 9887.278 788.415

1.3 JXL file

Supported Projection :

Projection Supported by Trimble Supported by Alteia
Mercator beta
Transverse Mercator
UTM beta
Lambert Conformal Conical beta
Oblique Mercator
Oblique Conformal Cylindrical
Oblique Stereographic
Polar Stereographic
RD Stereographic
Albers Equal Area beta
Cassini Soldner beta
Krovak
New Zealand Map Grid beta
United Kingdom National Grid
Denmark
Hungarian EOV
Stereographic Double
Rectified Skewed Orthomorphic (RSO
UPS North beta
UPS South beta
Projection Grid

Supported Datum Transformation :

Projection Supported by Trimble Supported by Alteia
No Datum
Helmert Three Parameters beta
Helmert Seven Parameters beta
Grid Datum
RTCM Grid

Supported Geoid Model :

Trimble Name Proj4 filename Supported
EGM96 (Global) egm96_15.gtx
GEOID12A (Conus) g2012au0.gtx
GEOID12A (Alaska) g2012aa0.gtx
GEOID12A (American Samoa) g2012as0.gtx
GEOID12A (Guam) g2012ag0.gtx
GEOID12A (Hawaii) g2012ah0.gtx
GEOID12A (Puerto Rico) g2012ap0.gtx
GEOID12B (Conus) g2012bu0.gtx
GEOID12B (Alaska) g2012ba0.gtx
GEOID12B (American Samoa) g2012bs0.gtx
GEOID12B (Guam) g2012bg0.gtx
GEOID12B (Hawaii) g2012bh0.gtx
GEOID12B (Puerto Rico) g2012bp0.gtx
Atlantic Canada HT2 HT2_0.gtx

2. Update the local CRS of an already existing site

It is possible to define the local CRS of a site from the info panel

In order to make the transformation possible, a global system must be defined previously

With this method we enabled the capacity to export older dataset into the local system as we now have the transformation with both systems.

3. Set the Local coordinates during Site Creation with images

If you create a site and upload images at the same time, you can also set the local coordinate :

Like mentioned above, the global site Coordinate Reference System must be also defined.

4. Data importation in local CRS

  • Vector : User can upload a vector file with the local CRS.
  • Raster : For the moment a raster file can only be uploaded as File in local CRS which means it will not be displayed on the map.
  • Point Cloud : Not supported yet in Local CRS

5. Data exportation in local CRS

Datasets can be export in Local CRS. Please click here to learn about exporting data on Alteia

In the download section, during the export, click on Switch to Local CRS.

  • Vector : users can export in local CRS
  • Raster : users can export in local CRS
  • Point Cloud : user can export in local CRS using the analytic Convert Point Cloud to local coordinates


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