Project Features

As default, ArcView (similar to any other GIS software) displays line and polygon features as a set of straight lines connecting the point co-ordinates defining the feature. When the source data are stored as decimal degrees, ArcView can project the points, but the lines are still straight. This is not always acceptable, e.g. latitudinal or longitudinal lines connecting point co-ordinates defining the zone vertices often define administrative zones. In a map using the Mercator projection (common for sea charts) latitudinal and longitudinal lines form a Cartesian co-ordinate system, and the default display using straight lines is correct. However, if one chooses to use more area- and/or distance-correct projection, the straight lines will deviate from the corresponding projected lines. To solve this problem, we have included a utility to project entire features, not just the vertex co-ordinates.

The utility will project all line segments (spanning more than 1° latitude or longitude) of the selected features in the active themes. If no features are selected in an active theme, the user is prompted to verify whether all features in the theme should be projected. New shapefiles including all features (selected/ projected and unselected/unprojected) from the active themes are created. The user is prompted for the name of each new shapefile. The original themes are deleted from the view and the new ones added. The new projected themes use the similar legend as the corresponding source theme, and the name is the same as the name of the source theme + the string 'projected'.

Note 1:

This utility will only work if the View has a projection.

Note 2:

Do not delete the shapefile with the unprojected features. The projected features are only valid for the projection they were created for. The resolution of the projected features is also scale-dependent. Hence, if you zoom in to a larger scale or you change the projection, you should start over again from the original feature theme. Remember also that you cannot reuse a shapefile that is included in the active project. Hence, to reuse one or several shapefiles with projected features, you must delete the theme(s) from the view and save the project. You must also add the original themes again and set up the proper legends. We recommend that you prepare all unprojected feature themes in a source project file, and that you import this project file into the project where you need to project the features.