Seeking help to summarize values for zone

[BobChristensen]

Greetings,

I have creates a deer habitat value raster that includes numeric fields for habitat values "before logging", "present condition" and the change in habitat values between the first two.

My project area includes 14 watersheds and I would like to use these watersheds as zones for comparing the sum of changes to deer habitat values for each watershed. 

I have tried the spatial analysis tool "tabulate area", using the watershed polygon as the zone layer, and the change in habitat values as the class field but that did not work like I was hoping, or I do not know how to make use of this new table so that after I join it to the watershed polygon I can classify using graduated colors to compare the sum of changes to deer habitat for each watershed. 

I attached the table mentioned above in case that is helpful. The column headers indicate the change in value and the cells indicate the area. I think I can get what I want using excel by multiplying the heading value with the area value and then summing for each watershed but I was hoping to do this calculation completely within arcgis pro.

Any help will be appreciated.

b

[XanderBakker]

I assume that both watersheds and deer habitats are polygon data (or do you have it as raster data)? Is each deer habitat completely comprised by a watershed? Could you provide a screenshot of the data or attach the data itself to this thread? 

The result you are looking can be obtained completely in ArcGIS without the need to pass the data to Excel. The data you obtained presumably represent the area of each deer habitat in each watershed and do not represent the change in habitat values. I'm still not completely sure about how to interpret the "change in habitat" values. What values do the "before logging" and "present condition" represent? In case these are areas and the data is in raster format, there areas that disappeared, could be represented by a pixel value 1 and you could use this in combination with the watersheds to do a zonal statistics (as tabel) with SUM to determine the total area of habitat that disappeared in each watershed. See How Zonal Statistics works—Help | ArcGIS Desktop 

[BobChristensen]

Hi Xander. The habitat data is in a raster form. The Zone data is a shapefile of watersheds. 

I have two columns in the habitat raster that indicate values in 1980 and 2018. Logging took place from 1985 to 1995. Logging does not zero out the habitat value, but it does reduce it so this is reflected in the 2018 column of the attribute table. The change in habitat is derived by subtracting 2018 values from 1980 values. 

I have been struggling with zonal statistics and how to get it to work for me. Does the info I provide above give you what you would need to help me with what steps I need to take to develop a table showing the summary changes in habitat value by watershed from 1980 to 2018?

b

[XanderBakker]

It would be so helpful to have access to the actual data and see for myself how the data is structured or at least provide a screenshot of the distribution of the data and of the attribute table of the habitat raster. Several questions remain unanswered, and I still don't understand what the actual habitat values are.

To explain little bit what doubts I have, a small example. You habitat data is a raster with an attribute table. Each record of the attribute table has a value in the field value. This is the value the raster has and what will be used if any raster calculations are performed. In this integer raster each unique value refers to a single pixel or a group of pixels that share in this case the attributes for habitat in 1980 and 2018. What actual values are used and what units are they in? 

If you would have two rasters (which you can achieve by using the Polygon to Raster—Help | ArcGIS Desktop tool), you could use Combine—Help | ArcGIS Desktop to create a raster where each combination of watershed and habitat result in a new record and you can join the watershed name and habitat data back to it a do you calculations in the attribute table and summarize by watershed.

In case you would have two polygon featureclasses (which you can create by using Raster to Polygon—Help | ArcGIS Desktop  on the habitat raster) you could use the Union—Help | ArcGIS Desktop tool to create a single featureclass where every combination of watershed and habitat results in a new polygon, followed by a similar process of summarizing the data.

To be able to use the zonal statistics tool the value raster should have the value you want to consider (not as attribute, but a value). This can be achieved by using the Lookup—Help | ArcGIS Desktop tool assigning the habitat change value to the output raster value followed by the zonal statistics as sum (depending on what the habitat values represent, what units they are in and if the area is something that should be taken into account).