GIS Mapping

Steps:

  1. Opening Shapefiles
  2. Selecting the Projection and Coordinate Systems
  3. Using Colorization
  4. Controlling the Layers

Introduction:

The goal of this tutorial is to provide you with a solid understanding of shapefile technology and to learn about the GIS-specific Canvas features. Before we start, you should take a minute and look over some of the more common GIS vocabulary and other industry terms.

For this tutorial, we are using shapefiles that we have downloaded from the USGS GEO-DATA Explorer site. The information for the coordinate system was provided in a map abstract.

GIS Vocabulary

Shapefile:

A shapefile is a geospatial vector data format for storing precise geometric locations and other associated attribute information.

Shapefiles consist of the following three separate types of files:

1. Main file: (.shp) shape format; the feature geometry itself.
2. Index file: (.shx) shape index format; a positional index of the feature geometry.
3. dBASE table: (.dbf), attribute format; columnar attributes for each shape.

Latitude is the angular distance of a point on the earth's surface along a meridian north or south of the equator. Latitude runs east to west.

Longitude is the angular distance of a point on the earth's surface east or west of the prime meridian. The Greenwich meridian is located in Greenwich England, thus the name. Longitude runs north to south.

A Meridian is a line of longitude running vertically from the north pole to the south pole. Unlike lines of longitude, meridians terminate at the poles.

The Prime Meridian is the line of longitude defined as 0.

A Projection is a method of representing the earth's three-dimensional surface as a flat two-dimensional surface. This normally involves a mathematical model that transforms the locations of features on the earth's surface to locations on a two-dimensional surface. Because the earth is three-dimensional, some method must be used to depict the map in two dimensions. Therefore such representations distort some parameters of the earth's surface, be it distance, area, shape, or direction.

There are three basic types of map projections: Azimuthal, conical, and cylindrical projections.

Step 1: Opening Shapefiles

To Open a Shapefile:

  1. Click File | Open.
  2. In the Open dialog box, locate your folder containing the GIS mapping information and make sure all of the 3 file types are present as per above (.shp, .shx and .dbf).
  3. Select the .shp - ESRI GIS Shape file and click OK. The Files/Layers List dialog box will open. Keep this dialog open to continue on in Step 2.

Tip: Canvas can either open or place shapefiles. When a shapefile opens, Canvas creates a default page size. If you wish to create a special custom page size, use the Place command.

Step 2: Selecting the Projection and Coordinate Systems

Shp files do not have coordinate system (CS) information embedded. However, some shp files come with Prj files, which do contain the CS information. Generally information about projection, earth model, or projection parameters is provided by the creator of the shapefile.  If the CS information is not available, Canvas will automatically deduce coordinate systems where possible, otherwise you will need to contact the supplier and set the projection manually.

To Select the Projection and Coordinate Systems:

  1. In the Files/Layers List dialog box, click the Projection button.

  2. In the File Coordinate System dialog box, do one of the following:

    • Leave the file coordinates as is.
    • Select a predefined CS.
    • Customize the CS (edit).
    • Load an external prj file.
  3. Once your coordinate system is established, click the Add button and navigate to any additional shapefiles.

  4. Repeat this process until you have added all of your Shapefiles.

Tip: Add more shapefiles at anytime by selecting GIS | Import.

Step 3: Using Colorization

You can use colors to quickly differentiate between the various shapefiles.

To Colorize Your Object Shapefiles:

  1. In the Files/Layers dialog box, select the first row and click the Properties button.
  2. In the Files/Layers dialog box, under Colorization, in the Method drop-down list, you can select either None, Solid Color, Color Range, or Color Array. For the first shapefile, we will use the Color Range method. Choose a color to start and end your gradient.
  3. Enter 5 into the Steps field, to ensure a gradual gradient.
  4. Click OK.
  5. Select the next row and click the Properties button. Choose the Solid Color method.
  6. Select the following row and click the Properties button. For this shapefile we will use the Color Array method and give it three shades of green. To do this, select a color from the pop-up color palette and then click Add. You can delete a single color by selecting it in the dialog box and then clicking Remove.
  7. Continue colorizing any remaining rows.
 

Step 4: Controlling the Layers

Since we used the Add button to open additional shapefiles, each shapefile is on a different layer, which gives us control of how the map is displayed.

You can use the Page and Layer controls to shuffle through the various layers.

Or you can also use the Document Layout palette to lock, delete, shuffle, and turn off layers.

All of the object's GIS information is easily accessible by selecting the object and opening the Object Properties palette under Windows | Palettes | Object Properties.