How to compute surface of green.

Koen_Haverkamp

I followed the instruction (How to compute the presence of a minimum amount of green - Tygron Support wiki) on the Wiki. The surface >200 square meter doesn't change in color in the combo overlay. Did somebody know a solution?

Rudolf

Hi Koen,

It sounds like you might not have configured the legend of the Overlay properly. Can you select the overlay in the editor, then on the right hand size click on the "Legend" tab, and see what colors and values are configured?

Can you click on a location in the world where you expect the "200 square meter" condition to be valid, and see how the legend of the overlay is configured to show that value?

Regards!

Koen_Haverkamp

In the meanwhile I have found the solution. Thank you for your respond, I was forgotten to enter the attribute to the average overlay.

Koen_Haverkamp

Now I have make a combo overlay, with the average overlay. I have copied the formula from:(How to compute the presence of a minimum amount of green - Tygron Support wiki) The result is red surfaces, which pretend the surfaces bigger than 200 m2. I have export the grid data and it seems that the red surfaces are not 200 m2, but smaller.

The second image is the exported grid to QGIS. Below the attribute tabel, with entry 1 the red surfaces.

My question is did somebody know how it is possible that not all red surfaces are above 200 m2.

Rudolf

Hi Koen,

I'll update the documentation to be more clear about this point.

What you see computed is not swaths of green which are a continuous 200m² or more. What you see is a highlight of all locations with 200m² of green in the direct vicinity. You can use this information as a "given" that, in that location, 200m² of green can be found, but not the exact extent of that 200m² of green.

Koen_Haverkamp

Thanks for your comment, this makes it clear.

Koen_Haverkamp

@Rudolf , would you happen to know how to calculate a continuous transect of green in stead of calculating 200m2 green in the area overall. The goal is to find a compact block of green to determine suitable habitat for a species.

At the moment a single tree or bush in this grid can be marked as suitable living space. However that is not desired.

My gratitude for your help.

Rudolf

Hi Koen,

At this time it is not possible to compute that in the Tygron software directly. This is due to the way the Tygron Platform rasterizes the Project area and the principle of calculation being more aimed at surface totality rather than the aggregation of individual elements.

The technique used allows for the computation of where locations exist which match your requirements, and not the exact extents. Depending on your use-case, propagating this information may be sufficient. Otherwise, I would be interested in knowing what your end-result requirements are so that I can help in considering an adequate solution.

An alternative may be a post-processing step in QGIS or FME, which contain tools for converting grid data into polygons. If you take the raw grid of (cool) green, and covert that grid to polygons, you will be able to compute the surface areas of those polygons, and inherently have their extent.

It is also possible to, when exporting grid data form the Tygron Platform, opt to turn the grid into legend polygons. However, when using this approach I explicitly recommend finding a method to simplify the polygons, due to the computational complexity of a polygon which follows the edges of a grid exactly.

Regards!