Running Geoprocesses

Geoprocesses are spatial computations done with the company datasets in the cloud server to extract additional information not provided in the regular Pathfinder interface. These processes are typically defined to serve advanced needs of specific customers, so they are not available for all companies.

If your company requires access to a geoprocess which is not available to you, contact Gilytics.

Note

Viewer users can not run geoprocesses, but they can add shared scenarios to see results generated by other users.

Access to Geoprocesses

If one or more geoprocesses has been enabled for your company, you can access them from the Results/Geoprocessing Tools menu:

_images/geoprocessMenu.jpg

When the geoprocessing dialog opens, you can select the geoprocess you would like to run. You can click on the “More” button for information about what each geoprocess does.

_images/geoprocessDescription.jpg

When a geoprocess is selected, some options will be displayed below. The specific options shown depend on the geoprocess.

Note that the geoprocess description also includes the outputs which will be generated, in this case the intersected geometries and a table with their attributes.

After selecting the input options, click on the “Process” button and check the process status in the log until it is completed:

_images/geoprocessLog.jpg

Note

The actual names of geoprocesses may vary, since they can be exposed with different names for each company.

Base Layer Features Intersecting Path

A common geoprocessing task is to find the objects crossing or near the calculated route. This geoprocess can be used to evaluate the impact of the proposed path on protected areas or find which properties are affected.

To execute it, we must select the base dataset (Base Layer) to intersect, the path already calculated in our project and the buffer distance: how close to the path can be the features to be considered “intersected”.

_images/geoproc_intersect.jpg

After running the geoprocess, we get the geometries of the intersected elements, which we can export, add as a layer in the project or display on the map, and a table with their attributes, which can be downloaded, for instance, to obtain IDs or names of the elements.

_images/geoproc_intersect_result.jpg

In this case, if we select to add the result as a layer, we will find the intersected features under the “Geoprocess output” category:

_images/geoproc_intersect_layer.jpg

Path Number of Crossings

In some cases, it is important to know how many times the candidate routes cross certain layers (railways, protected areas, etc.), since this may incurr in additional costs or restrictions.

This geoprocess provides the number of intersections between selected paths and layers:

_images/geoproc_numintersect.jpg

After running the geoprocess, we get a table in CSV format, showing how many times each path intersects each of the selected layers:

_images/geoproc_numintersect_result.jpg

Export Sub Corridor

The corridor map shows the areas closer to an optimal path. No data (transparent) areas show where the cost is too high or forbidden.

This geoprocess allows users to extract the valid corridor area near a calculated path (given a maximum distance), or extract the whole valid corredor area if the full corridor flag is selected.

In order to use this geoprocess, typically the user would select a corridor map from the project or an imported raster layer.

_images/geoproc_subcorridor.jpg

The result is a polygon geometry containing the valid corridor area, and maybe holes where the corridor is not valid:

_images/geoproc_subcorridor_result.jpg

Buffered Path Layer Coverage

In some cases users are interested in knowing the area affected by the route across different layers, assuming the path is expanded or buffered by certain width. For instance, if a path is crossing a forest layer, and vegetation must be trimmed near the route, the user may want to calculate the total area to be trimmed.

To do this, the user can select the path, the corridor width or buffer, and the layers whose coverage must be calculated:

_images/geoproc_area_options.jpg

The resulting corridor can be exported or displayed as a vector layer:

_images/geoproc_area_coverage.jpg

The areas covered on the selected layers (in square meters) can be exported to a CSV table:

_images/geoproc_area_table.jpg

Note that Pathfinder’s path analytics chart provides instead a linear coverage: the lengths and percentages of the path along different layers in the project.

Visual Impact from Observers

Geoprocesses can also generate raster data. An example are the visibility analysis processes, which work on a digital elevation model (the DEM automatically generated in the project can be used):

This geoprocess calculates a raster whose pixel values represent the number of objects in the layer that can view that location.

_images/viewshed.jpg

The following image shows an example. In this case, we have some recreation areas (green polygons) whose scenery visibility we would like to protect. After running the process, we generate a raster. The value of each pixel indicates how many of the areas can see it.

By adding this raster result as a project layer, we can display it with color shades (red in this case) whose intensity matches the visibility values, that is, darker red shades mean those points are visible from a greater number of recreation areas.

We can now compare this viewshed with the path location (purple colored line) to check its impact.

_images/viewshed_layer.jpg

After calculating the viewshed and adding it as a layer, we can assign it some resistance and then recalculate the results to make the route avoid the most highly visible areas.

Note

The cost of this geoprocess is proportional to the number of objects in the layer. We must avoid layers containing a large number of objects (like buildings), because the process would take a long time to complete. It is possible to use the clustering geoprocess or another grouping method to reduce the number of objects before running it.

Viewshed (GRASS GIS)

This geoprocess calculates a raster whose pixels are yes/no values marking the area visible from the selected route.

_images/path_viewshed.jpg

In this case the raster only has two shades: visible or not visible.

_images/viewshed_path.jpg

With this result, we can easily check which areas and elements are affected by the line, visible to them.

Note

This geoprocess is faster than the Visual Impact.

Hybrid Planning

More and more, combining multiple infrastructure modes or technologies to plan a single route is becoming an important requirement. For instance, it may be necessary to find an optimal powerline path which combines overhead and underground (earth cable) sections.

The hybrid planning geoprocess addresses this routing problem. Its requirements are:

  • The area where underground cables are preferred, the critical area, must be defined in a project layer.

  • One scenario must define the overhead constraints, but in such a way that the overhead line crosses the critical area. This section will be then substituted by an underground route.

  • The second scenario (subscenario) must define the underground cable constraints.

  • The Start point must be located outside the critical area. The End point can be either in or out this area.

_images/hybrid.jpg

This image shows an example of results, with a blue overhead section and a green underground section. Critical areas are displayed in a transparent red:

_images/hybridRouting.jpg

Combined Routing (Tunneling)

Similarly, in some countries it is important to combine overhead powerlines with tunnel segments. The tunnel planning geoprocess has been implemented to do so by using a custom version of the Pathfinder Explore algorithm.

This geoprocess uses three different scenarios, one for the conventional technology (typically overhead), a second one with the constraints defining the tunnel sections (usually should have a smaller resistance/cost than overhead for a high elevation, surface protected areas, type of geology, etc.), and a third scenario defining the cost of locating the tunnel entrance (usually must be away from populated areas, but not too far from transportation networks).

The geoprocess includes tunnel-specific constraints like maximum and minimum slope, and a maximum and minimum length for the tunnel sections.

_images/tunnelGeoprocess.jpg

The results can be displayed in the 2D and 3D views, where the tunnel sections are marked with dashed lines.

_images/tunnelView2D.jpg

_images/tunnelView3D.jpg

This video shows how to use the geoprocess to get combined routes with tunnels:

Path Resistance Analysis

In addition to the resistance profile chart, this geoprocess provides statistics about the total value and the variation of the resistance (taken from the resistance map) along the selected path. It is a convenient way to compare the “cost” of the paths calculated with similar constraints. It is also useful to estimate the resistance of a path in a different scenario from the one used to calculate it.

Note that the resistance values reported here will not include the angle cost and other constraints applied in advanced algorithms.

The path and the scenario are selected as input:

_images/geoprocResistance.jpg

The Results tab will show a button to download the table with the stats:

_images/geoprocResistanceOut1.jpg

_images/geoprocResistanceOut2.jpg

Note

Strictly speaking, the resistance values of two paths are only comparable when they belong to the same scenario (or two scenarios with the same layer resistances), and use the same algorithm, since different algorithms may calculate the total resistance with different methods.

Hilltops and Ridges from DEM

Pathfinder creates automatically a digital elevation model (DEM) for the project area. This DEM can be used to automatically detect terrain features like ridges and hilltops.

This geoprocess calculates the main ridge lines and hilltops, using some parameters set by the user:

  • Minimum ridge length: minimum length of ridges in meters. This parameter is used to avoid generating ridges that are too small.

  • Minimum distance between hilltops: similarly, we want to avoid hilltops that are too close, so we can specify a minimum distance in meters.

  • Hilltop cluster threshold: with this parameter we can ignore groups of nearby hilltops.

As with other geoprocesses, getting the right results might take some trial and error.

_images/geoprocRidges.jpg

As a result, we obtain separate layers with the ridge lines and hilltop points, which we can download or add as a layer to the project:

_images/geoprocRidgesOut1.jpg

_images/geoprocRidgesOut2.jpg

Once these results are added to the project, we can use buffered rings and resistance values to avoid ridges and hilltops in the routing.

Ridges (geomorphon)

This geoprocess follows a different approach, using an image processing technique to calculate the ridge lines.

These are the input options:

_images/geoprocRidgesGeomorph.jpg

These are the ridge lines (green) seen on the terrain:

_images/geoprocRidgesGeomorphRes.jpg

Clusterize Layer

This geoprocess can be used to group together elements into larger shapes, for instance, to find building groups representing populated areas.

The geoprocess has some parameters to specify the amount of objects to include in each group and the maximum separation distance in a group.

_images/geoprocCluster.jpg

_images/geoprocClusterOut.jpg

Geoprocessing Results

After the geoprocess is completed, open again the Geprocessing dialog and switch to the “Results” tab of the Geoprocessing Tools dialog to access the output data.

The results will still be available in this dialog if you reopen the project later on.

_images/geoprocessOutputDlg.jpg

Depending on the geoprocess, different types of output may be available:

  • Table output: it can be saved to local disk by clicking on the “Download” button

    For instance, in the case of the “Intersect Layer” geoprocess, the table contains the list of features intersected by the path, with their geometries:

    _images/geoprocessTable.jpg

  • Vector output: geoprocesses also generate spatial data in the form of points, lines or polygons. This output can be:

    • Downloaded in a GIS-compatible format (GeoJSON).

    • Displayed on the map by clicking on the “Show on Map” button. Notice that in this case the results do not appear as an item in the Layers panel, but they will be visible on the Map view.

      For instance, in the case of the “Intersect Layer” geoprocess, we can see on the Map the intersected objects:

      _images/geoprocessMap.jpg

      Click again on the “Show on Map” button to hide the results.

    • Added as a layer by clicking on the “To Layer” button. In this case the resulting data will be added to the project under a “Geoprocess Results” group, and they can be used in the scenarios as any other layer.

  • Raster output: it can also be:

    • Downloaded as a TIF file to be used in a GIS or CAD software.

    • Added as a raster layer to the project. For instance, in the case of the viewshed geoprocesses we described earlier, they would appear as a new layer:

      _images/raster_geoproc_layer.jpg

      After switching the visualization on, these layers are displayed on the view:

      _images/raster.jpg



Disclaimer: the scenarios depicted in this manual do not represent actual customer projects or infrastructure proposals, and are presented for demonstration purposes only.

For more help, please use the help chat in the application, or contact Gilytics.