Frequently Asked Questions

How do I georeference a floor plan using Cadcorp SIS?

Floor plans, stored as AutoCAD DWG files for example, are commonly in a local coordinate system whose origin is close to their data. SISfm can use these for most purposes, but for some purposes (such as way finding) all floor plans and site plans must be in the same coordinate system, and for display with aerial imagery such as Google Maps they must be georeferenced.

Plans can either be georeferenced in their original format (e.g. by using AutoCAD), or they can be georeferenced by transforming their coordinates in a Cadcorp SWD file, leaving the dataset files unchanged. If DWG files are currently being compiled directly, to do the latter compile them with DwgSaveSwd set TRUE, then add the georeferencing transforms to the SWD files, and subsequently compile those instead.

A separate FAQ topic describes how to georeference a DWG file using AutoCAD. Here we show how to georeference a floor plan using the Cadcorp SIS Desktop application. Step 6 uses the building links overlay of a site plan that is already georeferenced; this step can be replaced by using any other georeferenced data, such as aerial imagery, as it would need to be to georeference site plans.

  1. Open the floor plan SWD.
  2. Use Home / Map / CRS and select the Viewing Projection tab to see the viewing projection (or select the CRS icon in in the Position status bar). Here we assume it is Geocentric.
  3. Use Home / Map / Overlays, select the Dataset tab, then select each overlay to review its CRS in the Coordinates field. Here we assume they are all also Geocentric.
  4. Still in the Overlays dialog, select the first overlay whose dataset is to be georeferenced, select the Coordinates field and select the target CRS, e.g. MGA94.MGA zone 50. This overlay (and any others with the same dataset) will disappear from the view.
  5. In the Map control bar, right-click on this overlay and select Zoom Overlay. This will zoom to it and change the viewing projection to the target CRS. Note that if the Track coordinates checkbox is checked, the Position field will display "This position is not compatible with the CRS".
  6. Open the site plan SWD, which we assume is in the target CRS. In the Map control bar, right-click on its building links overlay and select Copy, then right-click on the floor plan SWD and select Paste Overlay, then close the site plan SWD.
  7. Use View / Window / Split Vertically, then in the Map control bar, right-click on the copied building links overlay and select Zoom Extents to display it in one pane.
  8. Select any item in the floor plan overlay (this identifies its dataset), then use Edit / Geometry / Arrange / Move Dataset: select a "from" position in the floor plan, then a "to" position in the building links overlay.
  9. The floor plan disappears from its pane, and appears in the building links pane. Slide the split divider over the blank pane to remove the split, and zoom in to the georeferenced floor overlay. If necessary, move the building links overlay up the list, by dragging it in the Map control bar or using Move Up in the Overlays dialog, to see the floor plan overlay above it.
  10. Repeat step 8 if necessary to improve the alignment. If any rotation is necessary, press Enter after selecting the "from" position to display the Transformation dialog and enter the rotation in anti-clockwise degrees in the Rotate about Z field.
  11. To georeference any remaining overlays, in the Overlays dialog select one that has been georeferenced, select Dataset Properties / Properties, and copy the value of the Coordinate Reference System (_projection$) property to the clipboard (this value will commence with "FITTED_CS[...").
  12. Then in the Overlays dialog select an overlay still to be georeferenced, select Dataset Properties / Properties, and paste the clipboard as the value of the Coordinate Reference System (_projection$) property. After closing dialogs, that overlay (and any others with the same dataset) will then also be georeferenced. Note that this can be done for all datasets of all floors of a building if they are all aligned.

If you need further assistance, please contact IFM Support <support@integratedfm.com.au>.