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GIS Mapping |
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The goal of this short tutorial is to provide you with a solid understanding of Shapefile technology and learn something 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. Question: What are Shapefiles? A Shapefile is a digital vector (non-topological) storage format that has been created specifically for storing precise geometric location and other associated attribute information. Shapefiles consist of the following three separate types of files:
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, called the Greenwich Meridian (0), runs through Greenwich, England. From the Prime Meridian, measures of longitude are negative to the west and positive to the east up to 180°, halfway around the globe. 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 a variety of map projections, but all are generally of three basic types: Azimuthal, conical, and cylindrical projections.
NOTE: Before we continue further we wanted to remind you that the features and options discussed in this tutorial will only be active if you have purchased and installed Canvas 9 GIS+. To upgrade to Canvas X GIS+ click here.
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STEP 1 Opening Shapefiles Next, locate and select the .shp file that you wish to open and click OK. The Additional Files/Layers dialog box will open. Remember that the file type that you select must be a SHP - ESRI GIS Shape file.
When a Shapefile opens, Canvas creates a default page size. If you wish to create a special custom page size you need to use the Place command.
STEP 2 Projection and Coordinate Systems 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. In the Additional Files/Layers dialog box, click the Projection button to open the File Coordinate System dialog box. The coordinate system that we will use for all the Shapefiles is:
A. Predefined or Custom Coordinate Reference System Select an option and click OK to return to the File Coordinate System dialog box. Select the Custom radio button to enable the origin and measurement menus. Select either North East, North West, South East, or South West as the Canvas 0,0 origin. Select a unit of measurement to be used in the file. For this tutorial, we are using "meter" as the unit of measurement. B. Map Projection: Select the Predefined radio button to open the Select Map Projection dialog box. Select one from the list. The related property and parameter values are displayed on the right. Click OK to return to the File Coordinate System dialog box. Select the Custom radio button and then click the Edit button to open the Map Projection dialog box. Select a projection from the list. Further customize the projection by entering the necessary values in the Parameters section. For this tutorial, "Mercator" is our selected projection. In the Parameters section, enter 0 in the Central Longitude and True scale Lat fields. When complete, click OK to return to the File Coordinate System dialog box. C. Geographic Coordinate Reference System Although the map abstract lists GRS 1980 as the datum, we will use the "WGS 1984" earth model for our example. The Angular units will be the default selection.
STEP 3 Additional Files/Layers Dialog Box
STEP 4 Adding Shapefiles NOTE: We recommend setting up the projection for the first file and then adding other files. Thus, the added Shapefiles will use the same projection. To add a file, click the Add button and navigate to the Shapefiles. Repeat this process until you have added all your Shapefiles.
STEP 5 Colorization Select the first row and click the Colorization button to open the Colorization dialog box.
In the Method menu you will have the option to select either No Fill, Solid Color, Color Range, or Color Array. For the first Shapefile, we will use the Color Range method as shown in the image. Enter 50 in the Steps field. Click OK after selecting the colors to return to the Additional Files/Layers dialog box.
Now select the second row and click the Colorization button. We will use the Solid Color method. For this particular Shapefile we will be using a light green color. Click OK to return to the Additional Files/Layers dialog box.
Select the third row and click the Colorization button.
For this Shapefile we will use the Color Array method and give it three shades of blue. Using Color Array, the selected colors are randomly applied as fills. 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. Click OK to return to the Additional Files/Layers dialog box.
Select the fourth row and click the Colorization button. We will use the Solid Color method. Select a shade of red and then click OK.
Now that the projection and colorization techniques have been established, we can click the Next button to move to the Document GIS settings.
Document GIS Settings The Document section at the top indicates the bounding box of the document. Deselect Auto to enter values in the Min Lat and Min Long fields. If you are unsure of the coordinates for the bounding box, select the Auto checkbox. Click Finish to open the Shapefiles.
STEP 6 Controlling the layers
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.
Note that all of the object's GIS information is easily accessible by simply selecting the object and opening the Object Properties palette.
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