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SurView Tutorial

Display attributes

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Display attributes

Because of the diverse nature of the types of data and data files that SurView deals with, there are three distinct ways to access the display attributes for the files:

Selecting Edit | Display attributes... brings up a dialog box that provides access to the display attributes of each file. Some files have more than one set of attributes, each with its own dialog box.


Survey Line Data (.SLD)

There are several attributes that are specific to SLD files:

In addition, SLD uses the same attributes used by BOB files to draw variable-size scaled dot maps (colour, style, scale factors).

SLD display attributes are discussed in greater detail on the SLD page.


Grids/Images (.GRX)

For 2 & 3-variable composite images, there are no display attributes - the files are assumed to contain RGB or CMY colour values ready to display.

For single-variable grids, there are two basic entities that control the appearance of the grid:

The palette file & optional remap table is specified in the GRX file that serves as a wrapper around the grid file. There is a single dialog box to manage the use of these files.

initial display
initial display

Step 1
The initial display shows the colour table as a series of parallel bars of equal height. This example uses an 89-colour palette. The associated data values for the current remap table can be seen by moving the cursor along the base of the colour table display. If the GRX file was not set up with an external remap file, the [min,max] range (read from the GRX file) is divided into N equal intervals, where N is the no. of colours in the current palette. This represents a linear remap table. In this example, the overall data range is [-0.08,9.82].

histogram for [-0.08,9.82]
histogram for [-0.08,9.82]

Step 2
A histogram of the data distribution can be accumulated by entering the desired [min,max] values and clicking New. After the histogram has been accumulated, the heights of the colour bars represent the amount of each colour. Note that this does NOT change the remap table. In the example, it is clear that although the absolute [min,max] of the data is [-0.08,9.82], the values above ~3 are spurious values.

histogram for [0,3]
histogram for [0,3]
& new levels

Step 3
With this knowledge in hand, the histogram is recreated using a range of [0,3] to eliminate the spurious values. This in itself will not change the display. Then the Range option is used to specify that the range [0,3] should be divided equally into 89 colours. The histogram now shows a good distribution of colours.

The Range option can also be used to specify:

"N1 colours up to value V1, N2 colours up to value V2, ..."

The Interval option can be used to specify:

"N1 colours at interval I1, N2 colours at interval I2, ..."

The Individual option can be used to view and/or edit the individual colours in the remap table.

In addition, a new palette file can be selected. If the no. of colours, does not match the current no. of remap levels, the remap table is discarded and the [min,max] range is divided into N equal intervals, where N is the no. of colours in the new palette.

The remap levels can also be saved in an external file for subsequent re-use.


Points (.BOB)

Points are displayed from .BOB files, usually created by importing points from a .DBF file. Each .BOB file can contain one of two distinct types of points:

dot map
variable-size dot map

Dot map
A very useful map of data distribution can be created by changing the symbol type, colours & styles and scaling the size of the symbol to the data values. This is a common display method for multivariable geochemical data.

point attributes
point attributes

Point attributes
The no. of styles of points in BOB files depends on the nature of the data. But each style has a set of attributes (symbol type, line & fill colours, size or scale factors, rotation angle, etc). While viewing the .BOB file of points, several of the attributes can be changed and the various styles can be enabled/disabled. All of the styles can be changed from a single general-purpose dialog box, except the scale factors.

point scale factors
point scale factors

Point scale factors
To edit the scale factors, from the dialog box, choose Scale (if enabled, for proportional-size dots) to bring up the dialog box that allows the scale factors to be edited.

The statistical distribution of the data is shown in the graph, either as a linear or log plot of 'normal quantile' (cumulative probability) versus the data value.

The scaling equation allows a selected [min,max] data range to be used to scale the symbol in a linear or non-linear fashion. Values that lie outside the scaling limits can be hidden or clipped.


Arcs/Lines (.ASX, .BOB/BLC)

There are two attributes for arcs (polylines):

Arcs (polylines) can be displayed by both .BOB and .SHP files:


Polygons (.ASX, .BOB)

There are 3 classes of attributes for polygons:

Polygons can be displayed by both .BOB and .SHP files:



Text (.BOB)

text attributes

The only way that text can be used to annotate a map is to put the text into a .BOB file, with appropriate (easting, northing) or (longitude, latitude) co-ordinates. Each text string is assigned a style (which has an associated size, rotation angle and colour) when the BOB file is created. While viewing the .BOB file of text, the colour can be changed and the various styles can be enabled/disabled.


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