topic Re: ESRI GRID file (ASC) in Python Questions

ESRI GRID file (ASC)

JosephLing — Mon, 04 Apr 2016 09:40:29 GMT

How to create an empty ESRI GRID file (ASC) based on the size of "Based polygon" with cell size 10?

Re: ESRI GRID file (ASC)

DanPatterson_Retired — Mon, 04 Apr 2016 09:55:00 GMT

https://desktop.arcgis.com/en/arcmap/latest/tools/conversion-toolbox/an-overview-of-the-to-raster-toolset.htm

is the conversion to raster toolset

the perhaps raster to ASCII https://desktop.arcgis.com/en/arcmap/latest/tools/conversion-toolbox/raster-to-ascii.htm

By an 'empty' one... do you mean one where the bounds are classed as no data, it is not clear what you are trying to accomplish

Re: ESRI GRID file (ASC)

JosephLing — Tue, 05 Apr 2016 20:54:11 GMT

Thanks for comment, empty I mean is new Grid and it can be with no data.

Re: ESRI GRID file (ASC)

DarrenWiens2 — Tue, 05 Apr 2016 21:35:26 GMT

I'm a little confused exactly what you're after here. ESRI GRID (raster) and ASCII (text) are two separate file formats.

You could create an ASCII file as easily as opening a text editor and start typing a file like the following, substituting your own values in the header and use the 'NODATA' value for the pixel values:

Re: ESRI GRID file (ASC)

DanPatterson_Retired — Sat, 11 Dec 2021 14:55:42 GMT

well you could exploit Darren's data and simply convert the nodata value to 1, then use the

ASCII to Raster—Help | ArcGIS for Desktop . You will obviously have to have the correct number of rows and columns and properly specify the location of the bottom left cell (center or corner) and the X and Y cell size (ie 10m for both)

You can cheat even further by using the ideas here.

NumPyArrayToRaster—Help | ArcGIS for Desktop

import numpy as np
import arcpy
LLcorner = arcpy.Point(500000,5000000) # x,y coordinate of the lower left corner, in this case the middle of a UTM zone
rows= 10
cols = 10
cell_size = 10
nodata = 0.0 # or whatever
a = np.zeros((rows,cols),dtype='float64') # or 'int32'
out_raster = arcpy.NumPyArrayToRaster( a, LLcorner, x_cell_size = cell_size, value_to_nodata = nodata)
out_raster.save(" path and name to raster) # specify and extension for non-esri grid formats such as tif

Re: ESRI GRID file (ASC)

JosephLing — Thu, 07 Apr 2016 02:14:49 GMT

Thanks all for that. Now the step 2 I wish to achieve is below:

Step 2

Once the ASC file in #1 above is created, I need to run the following formula on each of the grid cell.

First:

With reference from the point of interest, as shown in the "Based polygon" image below (with green square),

I want to run tan^-1(x/y)

(Grid point (x,y) will be in the center of each cell)

For Example:

Location of point of interest (0, 0)

tan^-1 of (75, 50) = 56.3 (value of one of the grid cell with reference from point of interest (0,0))

[If point of interest is 10, 10 in the map, then the X,Y calculated above will be 85, 60 in the map]

Second:

I need to calculate linear interpolation (which is not yet confirmed the formula)

Third:

Result A x Result B x [Some other value]

I am trying to figure out if there is other way to do, but thanks all in advance for reply.