topic Re: Create Fishnet in Data Management Questions

Create Fishnet

SophiNeuner — Fri, 26 May 2017 09:43:39 GMT

Dear all!

I have to create a fishnet (raster) with a certain extend. I have a .shp file which has the needed extend which i should use. But my collegue tells me that a cell size should be 2/3 degree (latitude) x 1/2 degree (longtitude). He gives me the example from:

https://gis.stackexchange.com/questions/116302/create-polygons-and-fishnets-of-specific-size-and-orientation-and-buffers

But for me that makes not really sense, because i have the extend from my .shp?
Does someone know what my mistake it? I started now within ArcMap to create a fishnet for the .shp with the data:

Data Type: Shapefile Feature Class
Shapefile: C:\DATEN_FINAL\xxx.shp
Geometry Type: Polygon
Coordinates have Z values: No
Coordinates have measures: No

Projected Coordinate System: ETRS_1989_LAEA
Projection: Lambert_Azimuthal_Equal_Area
False_Easting: 4321000,00000000
False_Northing: 3210000,00000000
Central_Meridian: 10,00000000
Latitude_Of_Origin: 52,00000000
Linear Unit: Meter

Geographic Coordinate System: GCS_ETRS_1989
Datum: D_ETRS_1989
Prime Meridian: Greenwich
Angular Unit: Degree

Like a spatial resolution for (deg lat x deg lon) 1/2 x 2/3 is needed but how can i combine this with the extention of my .shp?

Thank you so much in advance for your help!
Best,
Sophi

Re: Create Fishnet

JayantaPoddar — Fri, 26 May 2017 10:07:01 GMT

I hope your shapefile's extent is large enough for creating multiple grids in FishNet.

If you want to specify the width and height in Decimal Degrees, you need to reproject the shapefile to a Geographic Coordinate System (e.g. GCS_ETRS_1989 [WKID: 4258]) .

Then open a blank MXD > Add the new shapefile > Create Fishnet using the extent of the shapefile (Template Extent) with the desired cell_width (0.5) and cell_height (0.666667)

For number of rows and columns, keep it 0.

Geometry Type: Polygon

Re: Create Fishnet

SophiNeuner — Fri, 26 May 2017 10:18:56 GMT

Thank you!

Yes my .shp file is large enough. So than i use this .shp file with the new projection for the extent?
Or is the 2/3x1/2 the width and height?

Re: Create Fishnet

JayantaPoddar — Fri, 26 May 2017 10:27:29 GMT

First reproject to Geographic Coordinate System. This will ensure the map units are in Decimal Degrees.

Open a new map and add the reprojected shapefile.

Create FishNet with parameters cell_width : 0.5 and cell_height : 0.666667

Since the map units are in Decimal Degrees, the cell width and height will be 0.5° and 0.666667° respectively.

Re: Create Fishnet

JayantaPoddar — Fri, 26 May 2017 10:36:19 GMT

A screenshot of Create Fishnet Tool

Re: Create Fishnet

SophiNeuner — Fri, 26 May 2017 11:56:03 GMT

Yes thank you! Exactly what i needed!

Re: Create Fishnet

JayantaPoddar — Fri, 26 May 2017 12:33:27 GMT

Glad it helped!!!

Re: Create Fishnet

SophiNeuner — Fri, 09 Jun 2017 08:15:37 GMT

Just as an additional information:

I realized a little error here, the cell_width and cell_height has to be changed to cell_width (0.666667) and cell_height (0.5).
Because the longtitude is 2/3° and the latidude is 1/2°.

Best regards, S

Re: Create Fishnet

JayantaPoddar — Fri, 09 Jun 2017 08:59:51 GMT

Oh! The original question was the other way around.

But my collegue tells me that a cell size should be 2/3 degree (latitude) x 1/2 degree (longtitude).

The answer was based on that. Good to know that you realized the change in the values.