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SurView Tutorial

Picking features

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SurView's cursor

The 'hotspot' of SurView's cursor skyvan is the end of the 'stinger' on the nose of the aircraft.

The cursor is a 'replica' of the 'Skyvan' aircraft (manufactured by Short Brothers & Harland). The Skyvan was owned by the Geological Survey of Canada (Canadian registration CF-GSC) and was in continuous use for airborne gamma-ray spectrometry research & development from 1968 to 1995.

Pick mode

right mouse button pick mode
right mouse button configured
to pick polygons

You can query polygons, polylines, and points by 'picking' them with the right mouse button, but this will only work if the file has been enabled for picking the data preparer. Not all features can be picked. It's common to specify no pick action for rivers, lakes, boundaries - data types for which little or no useful information is available.

Depending on how the files have been set up by the data author, in response to a click, SurView might do any of the following pick actions:

Pick mode
In some GIS packages, a file or layer is activated for picking. In SurView, all files configured for picking are always active, but you can set a pick mode for picking:

with the right mouse button. If only one of these file types is being viewed, then the right mouse button will usually configure itself automatically to pick the appropriate type of item. However, if you are displaying more than one of these types of features, then you must use the Pick | Right mouse button pick mode menu item to configure the right mouse button for picking one of the three types of objects and to adjust the pick tolerance (for lines and points).

Pick tolerance
Note that the pick tolerance for polylines is adjusted automatically each time the scale of the picture changes (the computed value is about 1% of the current view width), but you may have to adjust the value in order to pick a polyline correctly.

Check all polygons/stop on first polygon found
SurView uses a 'point in polygon' test that can be quite slow, despite it being optimized, if there are a lot of polygons. To speed up the search, SurView assumes that most of the time, there will only be one file of polygons that can be picked. It also assumes that those polygons are mutually exclusive, i.e. that they don't overlap. Accordingly, the default pick mode for polygons is stop on first polygon found. If there are several files or if there are overlapping polygons, this should be changed to check all polygons. SurView will then check every polygon in every file. If the 'point in polygon' test finds more than one polygon, a popup menu will display the choices and one of them can be selected.


Picking flight lines (SLD)

SLD files contain multivariable airborne or ground Survey Line Data. SLD files can be used to draw flight lines & profile maps in the map view. A flight line can be picked with the right mouse button or by selecting the flight line from the list provided using the Profiles | Choose line by name menu item. After confirming the picked line selection, the stacked profile data for that line will be drawn in a new, separate window from the map view. More detail is provided in the SLD section.


Picking points, arcs (lines) & polygons

When picking points or arcs SurView will use the pick tolerance to find all points or arcs within the indicated distance from the pick point. For polygons, SurView finds all polygons (or the first one) that contains the pick point. If there is more than one feature that satisfies the picking criteria, the choices are listed in a popup menu that always appears in the upper left corner of the SurView window.

Once the selection of the feature has been made (either as a unique feature or picked from the list of possible features). SurView retrieves the list of pick actions enabled by the data preparer. If there is one pick action, it is invoked. If there are multiple pick actions for the point, they are listed in a popup menu. The location of the menu showing the available pick actions is controlled by the Pick | Pick action menu pops up at pick point option. If not enabled, the menu appears in the upper left corner of the SurView map window, otherwise it appears at the pick point on the map. Note that this does not affect the location of the popup menu of possible features, which always appears in the upper left corner of the map window.


DBF information display

DBF record display
DBF record for
picked feature

Most of the pick actions are relatively simple, but SurView has several ways to view and explore linked DBF files that are attached to a point, line or polygon feature.

The dialog box shows the record for the picked feature from the DBF file that is associated with the spatial data file:


select a table
select a linked table...
display records
...click Display to see the record(s)...
display all records
...or click Display All to see all of the data


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