Overlay analysis with ArcGIS

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The ArcGIS gives a scope of complete spatial analysis tools, techniques, and capabilities. Most GIS spatial analyst may utilize a few kinds all at once to take care of spatial issues. Following are the techniques for spatial analysis

  1. Temporal
  2. Proximity
  3. Overlay
  4. Statistical
  5. Network
  6. 3D

OVERLAY ANALYSIS

The overlay analysis is a long-standing strategy, and the genuine intensity of GIS lies to some extent in “overlaying” or simultaneously in a dynamic mapping environment. It is one of the fundamental ways for spatial relations to be made or distinguished through spatial overlay examination. Spatial overlay happens when separate informational collections are associated and seen together, which share the same area. A new data set recognizing spatial relations are the result of this mix.

The overlay analysis in GIS can investigate inquiries and discover answers to the spatial inquiries like, Where is the best spot to construct housing? A group of obviously disconnected elements – land cover, elevation, distance from existing streets, streams, and soil composition – can be demonstrated as layers, then analyzed.

For instance, with a land-use layer and a soil layer, the farming area created over-rich soil can be gotten from the two levels.

OVERLAY METHODS

There are typically two overlay investigation modes: Feature overlay (overlay focuses, lines or polygons) and Raster overlay.

  1. FEATURE OVERLAY

The input layer, overlay layer, output layer are the vital components of the feature overlay. The overlay function divides the input level features, where the features of the overlay level overlap. New zones where polygons meet are made. On the off chance that there are lines in the input layer, the lines are isolated where polygons go through them. The new feature is put away in the output layer — the original info layer remains the same. The qualities of overlay layer features and unique attributes of the info layer are doled out to the useful new features’ output layer.

FEATURE OVERLAY TOOLS

Overlay tools are in the Overlay toolkit of the Analysis toolbox.

1.Intersection

This tool makes another element class regular in the two classes from the intersecting elements.

2. Union

This tool makes another class of features by joining the qualities of each class.

3. Identity

This tool consolidates features areas that overlap identity attributes to make another characteristic feature class.

4. Erase

This tool creates a component class outside of the erase class from those features or parts.

5. Symmetrical Difference

This tool makes a class of features that are not common to any of the different features included.

6. Update

This tool updates the feature class or layer attributes and geometry by overlapping the update function or class.

RASTER OVERLAY

Raster overlay includes at least two distinct groups of information that are gotten from a common grid. Separate informational collections are generally given as mathematical values. These values are then numerically combined to make another arrangement of values for a solitary output layer.

Raster overlays are frequently used to make hazard surfaces, sustainability evaluations, and different strategies.

RASTER OVERLAY TOOLS

Raster overlay tools are situated in various toolsets in the Spatial Analyst toolbox.

  1. Zonal Statistics

For example, sums up values in the raster layer by zones (classifications) in another layer—  such as determine the mean height for each vegetation type.

  1. Combine

Allots value for every cell of the output layer dependent on single values from different input layers blends.

  1. Weighted Overlay

Computers overlay raster processes and allow weights to be relegated to every layer before adding (you can likewise indicate the equivalent impact to make an unweighted overlay).

  1. Weighted Sum

It overlays a couple of rasters, adds and increases each by its weight.

HOW TO PERFORM VECTOR OVERLAY ANALYSIS IN ARC GIS?

Set up the ArcMap project

  • Start – ArcGIS – ArcMap

  • Open ArcMap with a new map:
  • Add the required data from the main menu

  • Under overlay toolkit in analysis toolbox, select the required tool from the drop-down menu according to the need of analysis.
    g., Intersect

  • Double-click the Intersect tool to open its discourse and enter the parameter information

  • In the input feature class, select feature that might be ice sheets and slope files
  • In the output feature class, allot a specific name and location
  • The leftover boundaries – Join Attributes, XY Tolerance, and Output Type – are discretionary. Browse the Help for each boundary to decide if you are to leave the default or make a choice.

EXAMPLE

The picture below shows the result of the intersection on the right side. Where the grey indicated the slopes and blue indicated ice sheets. Resultant is the ice-sheet present on the specific slope.

To achieve your results, repeat the overlay steps as necessary for other tools as well.

HOW TO PERFORM SPATIAL OVERLAY ANALYSIS USING ZONAL STATISTICS IN ARC GIS?

Example: Using the zonal statistics tool to explores the spatial relationship between surface temperature and land-use category

  • Start – ArcGIS – ArcMap
  • Open ArcMap with a new map:
  • Add data layers ( raster features might be land-use landcover, temperature, rainfall, soil nitrogen content, slope, aspect, etc.

Raster or vector such as watershed polygons, administration boundaries, building footprints, etc.)

  • On the main menu, click on the Arctoolbox

  • From the arc-toolbox, click on Spatial analysis tool, then click zonal then select zonal statistics as table option
  • The zonal statistics table windows will be displayed

 

 

  • In the input raster or zonal data, select the raster file (for example, land use)
  • In zona field, select the land-use attribute field
  • In the input value raster, select surface temperature file
  • In the output table, give a specific name to it.
  • Click ok and wait for the process.

  • To see the results, click on the zonal table in the table of contents to open it.

  • Zonal table will be open in front of you, comprising Surface temperature values summarized by land use category.

The analysis of this tabulated information is your own choice. You can convert this table into excel from the arc-toolbox conversion tool using the table to excel tool.

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