Overlay graphics |
|
Overlay files contain lines, shapes, text, or images drawn on top of other data drawn on a map. Commonly, overlays represent leases, contours, roads, aerial photos, or comments. Overlay layers can also include geological information like contour lines, fault lines/polygons, or unconformities. "Overlays" and "Layers"Petra stores overlay data in a single overlay file (*.OVL). Each overlay file can contains up to 256 different layers of data. Think of a layer file as a single layer exported from an overlay file. Layer files can be loaded into any overlay file (actually loaded into memory and saved to an overlay file). Layers can be turned on or off easily by either using the Overlay Preferences (menu or toolbar icon) and double clicking specific layers, or by clicking on individual layers in the Quick List. Petra draws items at the top of the layer list first with items lower in the list being drawn last; in other words, layers at the top of the list will be covered by layers at the bottom of the list. Layers can also be saved to an external file and read as an Associated Layer Files, which can make keeping data updated in a multi-user environment much easier. Note: Each user sharing the same project will have their own copy of the overlay file in memory. While well and seismic data is drawn dynamically from the project database, other graphics, such as, land grid lines, lease outlines, culture, rivers and roads are displayed from layers in the overlay. Individual layers in Petra can be shown or hidden depending on the desired displayed. Overlay Files and Multiple UsersImportant: Never share overlay files between multiple users, each user should have their own file. Graphics in the overlay are loaded into memory. Once loaded, the overlay file is not accessed again unless the user saves the overlay file. Changes to the overlay data are made in memory only, not to the overlay file itself. Getting StartedAdvanced Tools |