topic Fishnet in AEC (Architecture, Engineering and Construction) Questions

Fishnet

BaranISCEN — Thu, 12 Jul 2018 07:06:52 GMT

Hello,

I am reporting back to this forum, since I have an issue with a tool in ArcGis: Fishnet. Briefly, I have a map and points. Ideally I would like to sub-divide the map in grids, relatively small, and then look at wether there are points and borders in the grid. At the end of the day, I want to see if the grids with borders contain more points than the others.

I looked on the internet and understood that the right tool was Fishnet. However, when I use Fishnet, the Output feature class does not appear in the Layers and I don't understand why this is so. I re-started several times but nothing change.

To create the Fishnet, I must precise that I took the shp. file on my desk (and not the Layer directly since this was not accepted) but I had to rename it. Then I put the template extent as the layer concerned, and put arbitrarily 50 and 50 for the height and width.

Then, there is the question of whether or not it is possible to calculate whether there is a line and points for each grid, but first there is the ouput feature class problem that I would like to solve - if you can help me.

Many thanks,

Re: Fishnet

DanPatterson_Retired — Thu, 12 Jul 2018 08:26:52 GMT

you seem to want to work with planar units (ie meters)

I suspect it is a coordinate system issue since it appears that the map is in decimal degrees and you tried to make a fishnet in the same coordinate system, meaning that 50, would be translated to 50 degrees by 50 degrees.

Project your map data (maybe a lambert conformal conic projection covering Europe), then specify your fishnet using the same coordinate system and your units in meters... but not 50 it will be way too fine

Re: Fishnet

BaranISCEN — Thu, 12 Jul 2018 13:22:52 GMT

Thanks a lot. That's actually what I did, but now I get this :

When I change the color to blank, I simply get again the starting map, but no grids.

Re: Fishnet

DanPatterson_Retired — Thu, 12 Jul 2018 13:40:59 GMT

you have no grid because 50 is being translated to 50 degrees and not 50 meters.

Going back to my original... what is the projection of your data? or is it even projected?

If you want to specify a grid in planar units, then use a projection. If you want to specify it in decimal degrees, then figure out the extent in decimal degrees, (say 10 degrees), decide how big you want the grid. perhaps 0.1, 0.05, 0.001 etc degrees...

Re: Fishnet

BaranISCEN — Thu, 12 Jul 2018 15:12:12 GMT

I am sorry. I was not clear. In fact, Fishnet does work while using degrees but I don't understand why I had to consider degrees units after having projected the map to Lambert and how I can use meters instead.

Re: Fishnet

DanPatterson_Retired — Thu, 12 Jul 2018 16:13:47 GMT

Show the extent (left, right, top and bottom) of a featureclass you want to lay over a fishnet.

Do this in a new dataframe with no other data especially a basemap

Re: Fishnet

BaranISCEN — Fri, 13 Jul 2018 14:30:24 GMT

Thanks a lot. Ultimately, I'd like to count for each grid if there is a point in the grid and a line, border. I was thinking that a way of a computing the number of points within each grid would be like counting the number of points within a polygon (https://webcache.googleusercontent.com/search?q=cache:uMcP7w3aZ0MJ:https://support.esri.com/fr/technical-article/0000085… ) but for the borders, do I have to to convert from polygon to line and do the same thing ?

Infinitely many thanks