How to georeference nodes

In Flood Modeller you can georeference non-georeferenced 1D cross sections, i.e. the cross sections which do not have the Easting and Northing coordinates specified for all the points of all or some of the cross sections in the model file, however in this case you need to have a gxy node locations file for this model. As mentioned earlier, using the procedure described here you can also georeference the models where some cross sections are georeferenced and some are not.

The steps for georeferencing a fully non-georeferenced model are:

1. Load your non-georeferenced model file (i.e. .dat or .sec file formats) into the Layers panel of Flood Modeller. Go to GIS Data > Add GIS Data in the Home tab and browse to the file and click Open. Alternatively load the model into the networks section of the Project panel and then drag the file from there onto the map view. Below is an example of a non-georeferenced cross section as shown in the River Section properties window:

   

2. Import a node locations file (as a new points shapefile). This can be either of the following:

   • 1D network GXY file listing each node with its type and easting and northing coordinates.

   • Text file listing all nodes in a comma separated format with field headings “easting”, “northing” and “nodea” (in this order). This file must have extension “.txt”.

   To load the file go to GIS Data > Add GIS Data in the Home tab, browse to the file and click Open. When prompted specify a name for a point shapefile into which the GXY file data will then be transferred (to enable it to be visualised in your map view). The GXY node locations file should reference all nodes in the non-georeferenced data file loaded in Step 1.

3. Double click on Geo-reference Cross Sections in Toolbox; Additional Model Build Tools > 1D Cross Sections.

4. A list of available points shapefile currently in your map view is displayed. Select the file representing your node locations data and click OK to proceed.

5. Review the geo-referencing by opening the Attribute Window (right click on model file in Layers panel and select Show Attributes from displayed menu), than double-clicking on any cross section on the list. The following window is displayed (initially with Elevation tab active, so select Node Attributes tab):

   

The changes made to your model file are automatically saved. However, if your network is also loaded in the project panel then you will need to refresh it here by clicking Save Network in the Home tab of the main toolbar.

Partial Georeferencing

In some cases a model may contain some georeference data but not be fully georeferenced, i.e. each section may only contain limited easting and northing data as shown in the example below (from River Section properties window):

In this case the partial georeferencing function in Flood Modeller can be utilised as follows:

1. Load model file as a new layer and put this layer into edit mode (as described above)

2. In this case georeferencing is based on the coordinates of the two furthest available geo-referenced points in the cross section, i.e. each cross section must contain at least two coordinate pairs. Flood Modeller automatically generates a line between these points and other points of the cross section are placed along this line taking into account the information from the model file about distances between points within this cross section.

3. When the georeferencing is complete you can review the results by accessing the cross section details via the Attribute Window (accessed from Layer Editor tab of main toolbar or by right clicking on file in Layers panel). Then to save these changes select one of the following options from the Layer Editor tab:

   • Save - saves revised model file to current filename

   • Save As - saves to new user specified filename, which can only be a river sections file (sec file)

   • Stop Edit (also available from Layers panel right click menu) – you will be prompted to save your model file if you try to exit edit mode when there are unsaved changes to your file.

Note that the undo feature will not be able to undo changes made prior to saving.

Related topics

More about River Section Nodes