How do I use field-collected data to create a GIS layer?
When DeLorme’s long-awaited handheld GPS receiver, the Earthmate PN-20, was released over a year ago, we couldn’t have anticipated the level of interest that the device would garner among XMap users. With the release of XMap 5.2, which offered support for the PN-20, professional users were quick to recognize the value of being able to transfer any map, GIS layer, or aerial image to a gadget that they could easily carry in their pocket.
As with most other handheld GPS receivers, the PN-20 also offers a low-cost method for collecting data in the field. This data can be in the form of location points, typically referred to as waypoints, or lines, which record the movement of the device and are referred to as tracks.
The Exchange function of XMap allows waypoints and tracks to be downloaded and displayed on the map. Waypoint and track layers are managed using the Draw tab tools, which include the option to change the appearance or symbolization of the objects as needed.
More often than not, these field-recorded locations represent more than just points or lines on the map; they usually denote the location to which an array of data or information is attributed. For instance, a point might represent a nesting site to which such data as species, nest condition, number of eggs, etc. is assigned.
In order to carry out this type of data mapping, the collected points or lines must be converted into GIS layers using XMap GIS Editor or Enterprise. The conversion process is very straightforward:
- First click the File button in the Draw tab and select the appropriate layer.
- To the right of the tab area click the Copy To button and choose GIS Layer. This opens the GIS Import Layer dialog box with the selected waypoint or track layer automatically added as the source file.
- Select a target database and click the Next button to begin the import process. The new layer will appear in the Workspace of the GIS tab.
Several attribute fields are automatically added to GIS layers that are created from data in the Draw tab. These include the label that was previously assigned, the type of symbol used to denote each object in the original draw layer and the date and time at which each object was created. Any or all of these attribute fields can be removed or deleted if needed.
The benefit of migrating field-collected data from their original draw layer format to the GIS tab is that additional data can now be added to each object. Attribute fields can created manually and the relevant data can be entered for each object in the layer. Alternatively, external data in the form of a spreadsheet, database file (.dbf), or several other formats can be imported and appended to the objects in the layer to automatically create additional attribute fields. These two functions are accessed by clicking Attributes button on the left of the GIS tab, clicking the Design View button at the upper left corner of the attributes table and clicking the Options button.
With the appropriate attributes added to each field-collected point or line, the data analysis tools of the GIS tab, such as the classification and querying tools, can now be employed to expose the spatial patterns in the data.
While the Draw tab in XMap provides an adequate level of functionality for simply representing a field-collected point or line on the map, you should consider using GIS tab to efficiently manage the data behind each point or line. Transferring data to the GIS tab is a simple as a couple of clicks of the mouse
