Django app that imports CAD drawings in Leaflet maps

Show CAD drawings in interactive web maps, download previously uploaded files with geo location, download CSV files with extracted data.

This app is tested on Django 5.1.1 and Python 3.12. It heavily relies on outstanding ezdxf for handling DXF files, pyproj for geographic projections, shapely for polygon verification, django-leaflet for handling maps, django-geojson for storing geodata, django-colorfield for admin color fields. The library relies on GDAL, which is system specific.

Activate your virtual environment and install with:

python -m pip install django-geocad

In your Django project add:

INSTALLED_APPS = [
    # ...
    "easy_thumbnails",
    "leaflet",
    "djgeojson",
    "colorfield",
    "djeocad",
]

# my_project/urls.py
urlpatterns = [
    # ...
    path('geocad/', include('djeocad.urls', namespace = 'djeocad')),
]

Migrate and collectstatic. You also need to add initial map defaults to settings.py (these are the settings for Rome, change them to your location of choice):

LEAFLET_CONFIG = {
    "DEFAULT_CENTER": (41.8988, 12.5451),
    "DEFAULT_ZOOM": 10,
    "RESET_VIEW": False
}

Add two lists to my_project/settings.py:

CAD_LAYER_BLACKLIST = [...]
CAD_BLOCK_BLACKLIST = [...]

Here you can store names of layers and blocks you don't want to be processed.

You also need a base.html template with following template blocks (a sample base.html is provided among package templates).

{% block extra-head %}
{% end block extra-head %}
...
{% block content %}
{% endblock content %}

Package comes with two templates, djeocad/drawing_list.html and djeocad/drawing_detail.html. Copy and override them in your project templates to add your styles.

Locally browse to 127.1.1.0:8000/geocad/to see a List of all drawings, where drawings are just markers on the map. Click on a marker and follow the link in the popup: you will land on the Drawing Detail page, with layers displayed on the map. Layers may be switched on and off.

To create a Drawing you must be able to access the admin with GeoCAD Manager permissions. You will also need a DXF file in ASCII format. DXF is a drawing exchange format widely used in CAD applications. Try uploading files with few entities at the building scale, as the conversion may be inaccurate for small items (units must be in meters).

If geodata is embedded in the file, the drawing will be imported in the exact geographical location. If geodata is unavailable, you will have to insert it manually: to geolocate the drawing you need to define a Reference point on the drawing of known Latitude / Longitude.

Mark the point on the map and eventually insert it's coordinates with respect to the DXF World Coordinate System origin (0,0,0). A good position for the Reference / Design point could be the cornerstone of a building, or another geographic landmark.

Check also the rotation of the drawing with respect to the True North: it is typical to orient the drawings most conveniently for drafting purposes, unrespectful of True North. Please note that in CAD counterclockwise rotations are positive, so if you have to rotate the drawing clockwise to orient it correctly, you will have to enter a negative angle.

Alternatively, you can select a Parent drawing, that will lend geolocation to uploaded file. This can be useful when you want to upload different floors of a single building.

Press the Save button. If all goes well the DXF file will be extracted and a list of Layers will be attached to your drawing. Each layer inherits the Name and color originally assigned in CAD. POINT, ARC, CIRCLE, ELLIPSE, SPLINE, 3DFACE, HATCH, LINE and LWPOLYLINE entities are visible on the map panel, where they inherit layer color. If unnested BLOCKS are present in the drawing, they will be extracted and inserted on respective layer.

In Drawing Detail view it is possible to download back the DXF file. GeoData will be associated to the DXF, so if you work on the file and upload it again, it will be automatically located on the map.

You can also download a CSV file that contains basic informations of some entities, notably Polylines and Blocks. Layer, surface (only if closed), perimeter, width and thickness are associated to Polylines, while block name, insertion point, scale, rotation and attribute key/values are associated to Blocks. If a TEXT/MTEXT is contained in a Polyline of the same layer, also the text content will be associated to the entity. This can be helpful if you want to label rooms.

You can modify geolocation and appearance of drawings, but the DXF will not be affected. If you want to modify the file, download it and use your favourite CAD application, then upload it back again (it will be already geolocated!).

Geodata can be stored in DXF, but ezdxf library can't deal with all kind of Coordinate Reference Systems (CRS). If Geodata is not found in the file (or if the CRS is not compatible) django-geocad asks for user input: the location of a point both on the map and on the drawing coordinates system, and the rotation with respect to True North. The pyproj library hands over the best Universal Transverse Mercator CRS for the location (UTM is compatible with ezdxf). Thanks to UTM, Reference / Design Point and rotation input, Geodata can be built from scratch and incorporated into the file.

Tests with unittest, 98% coverage, missing some special conditions in DXF extraction. Tested for Django 4.2 and 5.1 and Python 3.9, 3.10, 3.11, 3.12 versions.