[GIS] Merging two or more layers using ArcGIS for Desktop

arcgis-desktoparcmaplayersmergeshapefile

I am working with three clipped layers that are shown in the TOC. I created these layers from a large watershed shapefile. However, each clipped layer includes the layer before it and only expands on the one before it.

I was wondering is there a way that I could combine the three layers without using the same features more than once and also at the same time assigning them different values. Pretty much as it is shown in the image that I have provided. How can I assign each clipped layer different values without repeating a feature?

I have tried using the merge tool but then I don't know how to give each features different values.

This may be a little confusing please let me know if you have any questions

enter image description here

Best Answer

The option which will allow you to retain all of your data is Union. It will 'Intersect' two layers at a time spatially while retaining all the features. Attributes are concatenated together where features overlap.

You will, in the union method, be 'duplicating' your data. After you've completed the process, make sure to look through the attribute table to make sure you understand what's happened.

You can also to a pure Intersect, but this will exclude anything that is not overlapping. I only suggest this because it may be applicable to some of your analysis.

Related Solutions

ArcGIS Desktop – Copying Features from One Layer to Another

Again, as explained in your earlier question (Creating Layer for Selected Features, then Moving it using ArcGIS for Desktop?), layers are views, not data. You need to manipulate the underlying data to achieve your desired result, and there are two approaches you can take. Neither is 'right' - they both have valid reasons to use.

First, you can have one shapefile or feature class (in overly simple terms a feature class is just a shapefile inside a geodatabase) which contains both kinds of features. This is typically for types of the same feature as you describe - coniferous vs deciduous woodland. As long as the features are related in some way (they're all ground cover, or types of trees, or land uses) it can make sense to keep them in a single feature class. What distinguishes the two (or more) types of features is an attribute. Some shapes have an attribute (type) with a value of deciduous, some have that same type attribute with a value of coniferous. Right-click the layer and choose Open Attribute Table to see the attributes of each shape. From that window you can add fields/attributes (but not while in an edit session). When you've added what you want, you can change the values for each shape in that field while in an edit session. Be sure to save your EDITS which is different than saving your MAP. This method requires only one layer in the map to work with the data. You can set up the symbology of the layer (right-click layer, properties, go to symbology tab) to display features with different attributes differently - say dark green fill for coniferous and light green for deciduous.

The second method is to keep all shapes of a given type in their own feature class. With this method you do not need to worry about the attribute because all shapes in that feature class are the same type. You have to maintain two different feature classes or shapefiles. To work with all the data you need at least two layers in your map - one for each feature class. Again, they can be symbolized differently.

QGIS – Merging Multiple Point Layers with Common Fields to Create a Single Table

There is a possibility using a "Virtual Layer" through Layer > Add Layer > Add/Edit Virtual Layer....

Let's assume there are two point layers one called 'points1' and second called 'points2', see image below.

With the following query, it is possible to combine all layers into a single table.

SELECT
    "ID",
    "name2",
    "name3",
    "unique1" AS "unique1",
    NULL AS "unique2",
    geometry
FROM
    "points1"
UNION ALL
SELECT
    "ID",
    "name2",
    "name3",
    NULL AS "unique1",
    "unique2" AS "unique2",
    geometry
FROM
    "points2"

The output point layer with its attribute table will look like:

Best Answer

Related Solutions

ArcGIS Desktop – Copying Features from One Layer to Another

QGIS – Merging Multiple Point Layers with Common Fields to Create a Single Table

Related Question