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Generalize a Slope Surface

Question asked by jborgion Champion on Mar 30, 2020
Latest reply on Apr 8, 2020 by nnoman-esristaff

My adventure into creating and visualizing slope surfaces has moved into a third and possibly final chapter.  See Using arcpy to create slope surfaces  and Display A Slope Raster for chapters 1 and 2.  I have a complete slope surface for the Oquirrh Range ( pronounced oh-ker) which bounds the Salt Lake Valley to the west.  As you can imagine it took a bunch of data and a bunch of processing.  My goal in this whole exercise is to display where someone can build or can't build according to our slope ordinance which basically says, anything less than 25% is fair game; 25.1% to 35% you need to survey the property and show exactly where the building will take place, and finally anything steeper than 35% is off limits.

 

The complete slope model is now stored as a mosaic dataset, and the values range from 0% to 2535% .  I'd like to eventually end up with a polygon feature class that is depicts the three classifications described above.

 

1 = 'Go for it';

2 = 'Show us the survey' ;

3 = 'I can help the next person in line...'

  

My first question is generalizing the slope model to such a degree a reasonable approach? My second question is how do I make the calculations against the original slope? I'm not well versed in map algebra but what I do understand seems like a series of conditional statements such as:

 

if slope value <=25:
    new value = 1
else if slope value between 25 and 35:
    new value = 2
else:
    new value = 3 

 

How is such conditional written in map algebra? Can that interim raster be held in memory and then output to a polygon feature class on disc? (I think I have enough ram...)

 

Or is there a better way to achieve my goal?

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