How do you create a GRID in ArcGIS Pro, with the ability to summarise features within each square of the grid?

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03-05-2019 05:51 PM
MelissaLandewee
New Contributor II

Basically, I have points on the map with $ values, as well as polygons showing areas of risk.

I want to create a 20km by 20km grid over my map, and summarise the total $ value of all points within each square, and the percentage of the square that is taken up by the risk polygons.

Can someone please advise if this is possible in ArcGIS Pro, and what tool you would use to create the grid?

Thanks! 

11 Replies
DanPatterson_Retired
MVP Esteemed Contributor

options

Create Fishnet—Data Management toolbox | ArcGIS Desktop 

Generate Tessellation—Data Management toolbox | ArcGIS Desktop 

then

Summarize Within—Help | ArcGIS Desktop 

or Spatial Join plus other options, depends on what your data are like and what you need to summarize

MelissaLandewee
New Contributor II

Hi Dan,

Thanks for that! 

I need to set the grid squares at 20km squared - I wasn't able to find what the cell height and width referred to as anything that I entered over 1 was bigger than the map area that was looking at (State of Victoria, Australia - which I have a polygon for) and didn't have the option to change to metres / km or even see what the standard measurement is. 

I tried the Generate Tessellation tool and it has the option to select the shape type as square and size which I was able to select as square kilometres, however when I do this I get the following warning: 'WARNING  Converting areal units squaremeters to squareunknown not supported.'

Any suggestions would be great!!

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DanPatterson_Retired
MVP Esteemed Contributor

It sounds like you might be working with Geographic Coordinates (aka decimal degree data), or worse... an unknown coordinate system.

Make sure you map is set to a projected coordinate system suitable for your area.... anything other than web Mercator … 

MelissaLandewee
New Contributor II

Hi Dan,

Properties for the map are decimal degrees with the coordinate system being GCS GDA 1994.

Am I able to work with this to create a grid that is 20km by 20km?

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DanPatterson_Retired
MVP Esteemed Contributor

at some stage you are going to have to specify a Projected coordinate system in order to get planar areas

ie

Generate Tessellation—Data Management toolbox | ArcGIS Desktop 

and similar approach when using Fishnet

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curtvprice
MVP Esteemed Contributor

Make sure you map is set to a projected coordinate system suitable for your area

The map is not what needs to be projected - the coordinate system used for the geoprocessing must be set to a projected coordinate system (ie UTM, Australian National Grid, whatever) where the units are meters (NOT degrees). 

Melissa, your best bet is to use the Project tool to convert your points and polygons to an appropriate projected coordinate system and generate the fishnet using one of those datasets that covers the study area to define the extent. Here's an example coordinate system: GDA94 / Vicgrid94: EPSG Projection -- Spatial Reference (WKID 3111)

vicgrid map projection

MelissaLandewee
New Contributor II

Hi guys,

I haven't done this before - can you suggest a projected coordinate system to use to be able to display as square kilometres?

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DanPatterson_Retired
MVP Esteemed Contributor

A projected coordinate system like the one suggested, has the units of meters, hence area will be in m^2, which can be displayed and/or calculated to km^2.

Have you tried projecting the polygon grid? the Shape_Area field will be in m^2... easy conversion from there

curtvprice
MVP Esteemed Contributor

Melissa, I suggested one optimized for Victoria that has xy units of meters. With the fishnet tool, provide a grid cell size in meters, ie 20000 for 20 km polygon grid cells.