This tool allows to manage the geolocation of the objects of the network (nodes, points of preemption of the reaches also called midpoints, cross sections).

The upper part of the "Geolocation" tab allows you to process the nodes and midpoints of the reaches (also called preemption points since they allow you to select a reach, to edit its parameters or view the results).

The "Compute pxl -> geo" option will use the pixel data (x-y position of the graphic objects on the 2D plan drawing) to calculate the geolocation (lat-lon) of the processed objects (nodes and preemption points here). This will be done using the geolocation of the upstream and downstream nodes of the selected area. You must therefore enter this before using this option. This is done by simple proportionality relationships between x-y and lat-lon (known as the rule of 3). This geolocation data will then be stored in the corresponding fields of the corresponding objects.

The "Compute geo -> pxl" option will do the opposite, that is to say position (x-y) the objects on the 2D plan drawing taking into account the geolocation data (lat-lon), while retaining the upstream nodes and downstream as references (x1-y1 and x2-y2) and using simple rules of 3 to calculate their positions. You must therefore position these upstream and downstream points where you want them, for example on a previously imported base map (see the dedicated page). This data will be stored and the node and midpoint objects will then be drawn at these locations on the 2D plane.

The lower part of the "Geolocation" tab allows you to process cross sections. This option is close to the previous one in the ideas behind "Compute pxl -> geo" and "Compute geo -> pxl". However, the reference points will be taken for each reach with its upstream node and its downstream node (and not, as previously, the upstream node of the selection and the downstream node of the selection). You must therefore have previously processed them with the options in the upper part of the tab, detailed above. In addition the positions (x-y) of the cross sections will be calculated with the "Compute geo -> pxl" option, and drawn thus just after launching this calculation (clicking on the corresponding button). But since the reaches are drawn on the 2D plane as 2 line segments between the upstream node and the midpoint then the midpoint and the downstream point, and that the cross sections are drawn and distributed on these segments according to their longitudinal abscissa within their reach (the coordinates of the x-y pixels will therefore be recalculated on each display), this detailed plan drawing of the sections will not be drawn like this on subsequent displays.

Further evolution of SIC allowing more segments and potentially as many as cross sections would handle this more aesthetically.

In this management of the geolocation of cross sections, we must also provide other information, since the entire cross section is geolocated (only 1 lat-lon data for each section) and not the various points of the section. However, a section seen up close is not a local object, but made up of a set of points (and can be several hundreds of m or km long). It is therefore necessary to indicate to what point the given geolocation corresponds, as well as how the section is located in relation to this geolocation point, laterally and angularly. The angle is given in relation to a reference indicated in the global geolocation options (Edit/Network Properties/Geolocation Settings), with the choices of Geographic North, the central line of the reach or the segment drawn within the reach . The “lateral abscissa Y” is given in the case of the choice “for a given lateral abscissa”). If we check the boxes for these values ​​they will be filled in for the corresponding objects when launching the "Compute pxl -> geo" calculation. Currently this data is stored but is not taken into account when drawing cross sections (to be done in a later version). For the moment the angle used for the drawing is 90° relative to the segment, and the assumed geolocation point is the central one of the section.

At the bottom of the tab we indicate a scale in X and Y, making the correspondence between lat-lon and x-y. These fields allow you to visualize these scales after using one of the 2 modification options above, but not to force a drawing to a given scale (these are output variables, not calculation inputs). As indicated by the tooltip when positioning the mouse on the corresponding fields, the values ​​indicated are the number of pixels for 1 degree of angle.

An example of geolocalized project is given at:
\dat\ex30_garonne\Garonne_benchmark_MinMoy_v4.xml