GIS

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Enabling GIS Extensions

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If you have already activated your GIS extensions, or are using one of the CED computers but the various extensions are not loading (Spatial Analyst, etc), you can just enable the extension by performing the following steps.

1. From in ArcMap, go to the Customize Menu

2. Then goes to the "Extensions" menu and just select the different extensions you with to enable.

3. Then hit close and your extensions should now appear in the toolbar.

See the following document for screenshots.

Saving Relative Pathways

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Ever run into problems with linked data getting broken? See this PDF for a potential solution to the problem.

Projecting XY Coordinates from spreadsheet

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See the attached PDF for details on how to project XY data that is provided in a spreadsheet.

Attachments

Projecting data in a different coordinate system

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See attached PDF for details

Difference between Projected and Geographic coordinate systems

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Difference beteween Projected and Geographic coordinate systems
a. Geographic Coordinate System (GSC):

A global or spherical coordinate system such as latitude-longitude. These are often referred to as geographic coordinate systems.
A geographic coordinate system (GCS) uses a three-dimensional spherical surface to define locations on the earth. A GCS is often incorrectly called a datum, but a datum is only one part of a GCS. A GCS includes an angular unit of measure, a prime meridian, and a datum (based on a spheroid). The spheroid defines the size and shape of the earth model, while the datum connects the spheroid to the earth's surface.

b. Projected Coordinate System (PCS)

A projected coordinate system such as universal transverse Mercator (UTM), Albers Equal Area, or Robinson, all (along with numerous other map projection models) provide various mechanisms to project maps of the earth's spherical surface onto a two-dimensional Cartesian coordinate plane. Projected coordinate systems are referred to as map projections.
A projected coordinate system (PCS) is defined on a flat, two-dimensional surface. Unlike a
GCS, a PCS has constant lengths, angles, and areas across the two dimensions. A PCS is always based on a GCS that is based on a sphere or spheroid. In addition to the GCS, a PCS includes a map projection, a set of projection parameters that customize the map projection for a particular location, and a linear unit of measure.

c. Why does it matter how you project the data?

i. Whether you treat the earth as a sphere or a spheroid, you must transform its three-dimensional surface to create a flat map sheet. This mathematical transformation is commonly referred to as a map projection. A spheroid cannot be flattened to a plane any more easily than a piece of orange peel can be flattened—it will tear. Representing the earth's surface in two dimensions causes distortion in the shape, area, distance, or direction of the data.

A map projection uses mathematical formulas to relate spherical coordinates on the globe to flat,
planar coordinates.

Different projections cause different types of distortions. Some projections are designed to
minimize the distortion of one or two of the data's characteristics. A projection could maintain the area of a feature but alter its shape.

Need some advice on picking the right coordinate system? Check out this article to help pick between some of the more commonly used ones in North America.

Define Coordinate system without a spatial reference

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Defining a Coordinate System of data without a spatial reference

Once you have identified the coordinate system of the data, you can define the coordinate system using the “define projection” tool.

i. ArcToolbox > Data Management Tools > Projections and Transormations > Define Projection
II. NOTE: This tool DOES NOT create a new data layer as an output. It modifies the existing data layer so you must make a copy before using this tool.

Exporting from Arcmap to sketchup

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See the attached file for details on how to take your Arcmap document and export it for use in Sketchup

Adding a new field in the attribute table

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ArcGIS allows you to modify the structure of shapefiles and dBASE tables by adding and deleting fields or attribute columns. The name and data type of an existing field can't be modified; instead, you must add a new field with the appropriate name and data type. A field's name must be no more than 10 characters in length; additional characters will be truncated.

A shapefile's FID and Shape field and a dBASE table's OID field can't be deleted. The OID field is a virtual column created by ArcGIS software when accessing the table's contents; it guarantees that each record in the table has at least one unique value. Shapefiles and dBASE tables must have at least one attribute field in addition to the FID and Shape fields or the OID field. After adding fields, you must start an edit session in ArcMap to define their attribute values.

The field data types supported by ArcGIS are discussed in Geodatabase field data types. The data mapping section in How data converts when importing has tables that show how data types for several data sources are mapped to the ArcGIS geodatabase field data types.

Adding a field in ArcMap

In ArcMap, right-click the shapefile layer in the table of contents and click Open Attribute Table.
Click the Options button and click Add Field.
Type a field name in the Name text box.
Click the Type drop-down arrow and click a type.
The properties that are appropriate to the new field's data type appear in the Field Properties list.
Click in the Field Properties list and type the properties.

Properties may include

Precision—The number of digits that can be stored in a number field. For example, the number 56.78 has a precision of 4.
Scale—The number of digits to the right of the decimal point in a number in a field of type float or double. For example, the number 56.78 has a scale of 2. Scale is only used for Float and Double field types.
Length—The length of a text field specified in characters
Click OK.

For a printable copy, download the attached PDF.