This section describes the Overlay Control Center dialog (pictured below). This dialog serves as the central control center handling all currently loaded data sets (overlays).
Currently Opened Overlays
This is a list of the all currently opened overlays. You can select an overlay by clicking on its name. Multiple overlays can be selected using the shift and control keys while clicking on overlays in the list. If the overlay is currently hidden, it is indicated to the left of the overlay description. Double-clicking on a layer automatically brings up its Options dialog. If you hold down the 'M' key while double-clicking the Metadata dialog for the layer will be displayed instead.
You can right click on the list of currently opened overlays to display a list of options available to perform on the selected overlays. Examples of available options include the following:
Create Elevation Grid from 3D Vector Data
- Create Elevation Grid from 3D Vector Data - This allows you to create an elevation grid from part or all of any vector features in the selected overlays that contain elevation data.
- Modify Image Position - This allows you to reposition imagery and vector data that was not correctly positioned when loaded, including imagery that was manually rectified. See the option below if you just want to shift an entire layer by some distance.
- Setup What Zoom Levels to Display Selected Layer(s) At - This option allows you to control what zoom levels/scales that the selected layer(s) will display at. You can choose to have layers only display below a certain zoom scale or between scales, or when the map is a certain percentage of the map display size or the map resolution reaches a certain level.
- Shift Selected Layer(s) a Fixed Distance - This option provides a quick way to shift any layer some fixed distance in any direction. When selected a dialog is presented allowing you to specify the distance to shift the selected layers in the X and Y direction or some distance along a particular bearing.
- Scale Layer Based on Actual Length of Selected Line - This option allows you to scale a selected layer based on a user-specified length of a selected line feature in that layer. This is useful if you know the actual length of a line feature in a vector layer and want to scale the layer so that the line length is correct without caring about where on the earth the layer is placed. The line that you know the length of should be selected with either the Feature Info or Digitizer Tool.
- Create Workspace File from Selected Layer(s) - This option allows you to generate a workspace just containing the selected layer(s) and their display options. This workspace can later be loaded with the File->Load Workspace menu command.
- Create Map Catalog from Selected Layer(s) - This option allows you to generate a map catalog file containing the selected layer(s). This map catalog can later be loaded with the File->Open Data File menu command.
- Zoom to Selected Layer(s) - This causes the view to be zoomed such that the full extents of the selected overlays are visible.
- Zoom to Full Detail For Layer - This causes the view to be zoomed such that a single sample/pixel in the selected overlay will take up approximately one pixel on the screen.
- Set Group to Assign to Selected Layer(s) - This allows you to specify a group to assign the selected layer(s) to. If layers are in a group, they will be organized under that group name in the Control Center and you can easiliy collapse them into a single item in the list of layers and operate on all items in the group by selecting the parent group item.
- Create Area Features From Selected Layer Bounds - This causes new rectangular area features with the name of the overlay as the display label to be created for each selected layer in the User-Created Features Layer. This is useful for creating an image index as the filename of the layer will also be saved as an attribute of the area feature created from it.
- Create Point Features at Elevation Grid Cell Centers - This causes a new layer to be created for each selected elevation grid layer with a spot elevation point feature at each grid cell center location. This provides a handy way to edit elevation layers as you can edit the elevation attribute of the created points or remove bad points, then create a new elevation grid from the layer.
- Create Area Features from Equal Values in Selected Layer - When a single raster or elevation grid layer is selected (with the exception of online sources), this option appears and allows you to create area features covering each distinct color or elevation value encountered in the raster file. This is useful for automatically creating areas for things like land cover raster files in a vector format.
- Find Extreme (Min/Max) Elevation Values in Selected Layer(s) - This scans the selected elevation grid layers to find the minimum and maximum elevation values and reports both the values and their locations to the user. The complete list (up to 10,000 shared location) will be saved to a file, and a shorter list presented to the user.
- Change View Shed Layer Color - This allows you to edit the color used to display the coverage area for a selected view shed layer.
- Edit View Shed Parameters and Recalculate - This allows you to edit the calculation parameters for a view shed layer and then update the results.
- Open Selected Map Folder in Windows Explorer - This causes the Windows Explorer application to be opened to the folder containing the selected map file.
- Split Into Separate Layers Based on Description/Attribute Value - This option allows you to create new layers by splitting the selected layer(s) into new layers based on a particular attribute value or by the description, type, or name of each feature. The new layers will be grouped together using the name of the original layer unless the original layer was already in a group.
- Allow Feature Selection from Selected Layer(s) - This option controls whether or not vector features from this layer can be selected using either the Feature Info or Digitizer Tools.
- Select All Features in Selected Layer(s) with Digitizer Tool - This option causes all features in the selected layer(s) to be selected with the Digitizer Tool.
- Close All Hidden Layers - This option causes all layers that are currently marked as hidden (i.e. have their display checkbox unchecked) to be closed.
- Hide All Offscreen Layers - This option causes all layers that are currently completely off of the main map view to be marked as hidden (i.e. have their display checkbox unchecked).
- Reorder Maps by Resolution/Description/Location - This option displays a dialog allowing you to choose a method by which to reorder the maps in the list. This includes sorting alphabetically, by resolution, or spatially sorting the maps.
- Move Selected Overlay(s) Up/Down - These options allow you to modify the order in which overlays are displayed in the main view. The large arrow buttons on the right-hand side of the dialog also perform these functions.
Selecting the Create Elevation Grid from 3D Vector Data option on the popup menu that appears when right-clicking on vector layers in the Overlay Control Center displays the Elevation Grid Creation Options dialog, pictured below. Using this dialog, you can configure how you want the elevation grid to be created using the selected vector data as well as what portion of the selected overlays to use when creating the elevation grid. You can also use the Gridding tab to specify that your data should be gridded in sections. This makes it possible to grid data sets that are too large to grid all at once.
The following options are also available when generating the grid:
- Use 3D Line Features as Constraints (i.e. Breaklines) - If this option is checked, any line and area features that have elevation values associated with them will be treated as constraints/breaklines. This will ensure that elevation values along the line/area boundary will be consistent with the elevation that should be along the line.
- Flatten 3D Area Features - If you have any area/polygon features with elevation in the selected layers that you are gridding, they will be treated as flattened areas rather than just additional 3D data points/constraints. This allows you to create flattened areas like lakes and also nice terrain surfaces from things like building models. If only 3D area features are present, any grid locations outside of the areas will be marked as invalid, otherwise the grid locations within areas will just be flattened to the area heights and the remainder of the grid will be generated as usual.
- Taper 3D Area Features Using Curve Value - If you have any area/polygon features with elevation in the selected layers that you are gridding and you also checked the option to flatten 3D area features, the taper option allows you to specify that rather than making the areas absolutely flat, the edges should be tapered with the area elevation existing near the centroid of the area and the elevation applied for the area dwindling to zero as you reach the area edge. The curve value specifies the exponent to apply to the percent distance a sample location is between the area centroid and the area edge to adjust the height applied at that location. Values less than 1 will make the edge steepness progressively greater (i.e. flatter at the middle, then steep edges), while values larger than one cause the steepness to be near the area centroid and flatter towards the edges, while a value of 1 provides for a linear taper. For example if you want to simulate a sand bunker for a golf course, a value of around 0.5 provides a decent simulation of a bunker.
- Ignore Zero Elevations - If checked, this option will cause any features with an elevation value of zero to be ignored. This is useful if you have a data set where features with no known elevation are marked with an elevation of zero.
- Save Triangulated Network (TIN) as a Vector Layer - If checked, this option will cause a separate vector layer with area features for each 3D triangle created as part of the triangulation and gridding process. This is known as the TIN surface.
- Heights Relative to Ground - If you check this option, all elevation values from the selected vector layers will be treated as relative to the height of any loaded underlying terrain surface (like a DEM). This is very handy for doing things like creating building models where you just know the building height above ground and not above sea level.
- Fill Entire Bounding Box Instead of Just Inside Convex Hull - If you check this option, the generated elevation grid will contain valid values filling the entire bounding box specified for the gridding operation. Otherwise, the valid values will only fill out to the convex hull polygon of the data being gridded.
- Export Grids Directly to Global Mapper Grid Files - If checked, this option will cause the generated elevation grid file(s) to be directly exported to Global Mapper Grid (GMG) files. This is useful when you are triangulating and gridding a very large collection of data and also using the Gridding tab to split the operation into smaller pieces. By directly exporting the results to GMG files you can create elevation grids that normally would not all fit into memory.
Pressing the Metadata... button displays metadata for the selected overlay. The actual metadata dialog displayed depends on the type of the selected overlay. The metadata dialog for a SDTS DLG is shown below.
Pressing the Options... button displays a dialog containing the available display options for the selected overlay(s). Options can be set on multiple raster or elevation overlays at the same time. The available display options depend on the type of the selected overlays. The following display options are used:
Vector Data Options
Selecting the Options... button while a vector (i.e. SHP, DXF, E00, etc) overlay is selected displays the Vector Options dialog (pictured below).
Feature Types/Labels/Elevations Tab
The Feature Types/Labels/Elevations tab provides the ability to specify which attribute field(s) (if any) to display as the name of features loaded from the vector file. You can also select which attribute field (if any) to use for the "elevation" value for the layer. By default, several attribute field names (like "ELEVATION", "ELEV", "ALTITUDE", "Z", etc.) are checked when an elevation value for the feature is needed. This option allows you to override this behavior and manually select the attribute to use. You can also select what units to assign to unspecified elevation values for the layer, such as per-vertex elevation values for 3D line and area features in the layer. Finally, there are also options available to select the classification to apply to unclassified area, line, and/or point features in the layer.
Area, Line, and Point Styles Tabs
The Area Styles, Line Styles, and Point Styles tabs provide the ability to customize how area, line, and point features found in the selected layer(s) are displayed. The following style settings are available:
- Use Default Style Based on Classification or Custom Stlye - This option is the default and specifies that features should be drawn and labeled using either the custom style applied to each feature, or the default drawing style for the classification assigned to each feature. You are configure the default drawing style for any particular classification on the Area Styles tab of the Configuration dialog, the Line Styles tab of the Configuration dialog, or the Point Styles tab of the Configuration dialog.
- Use Same Style for All Features - This option specifies that all features in the selected layer(s) should be drawn with the same drawing style, regardless of type or any custom style applied.
- Apply Styling Based on Attribute/Name Values - This option provides a way to base the drawing style on the value of a particular attribute. This is a powerful feature allowing you to assign a style to a particular value for a particular attribute. Any features whose value for the selected attribute/name matches the selected value will be assigned that style. If you have numeric values and the Interpolate Colors Between Numeric Values option is checked, any numeric values for the selected attribute/name that do not exactly match a value will find the two closest numeric values and interpolate the color values in between those numbers. Any features that do not have a matching attribute/name value will use the default style assignment for their type or the custom style if one has been set. You can also use wilcard (* and ?) characters in your attribute value to match on values matching some pattern. If you want to initialize the list of attribute values and styles from those attribute values found in the selected layer(s), press the Init from Values button.
- Assign Random Colors to Features - This option specifies that each feature shall be assigned a random color, either from the full set of 24-bit colors, or from a collection of colors specified by the user in a palette. You can use the Select Base Style button to assign the base style whose color will be randomly assigned. For areas, if the selected style uses no area fill, then the area border color will be varied rather than the fill color. For point features, you need to have a dot or custom shape (like dot, diamond, square, etc.) selected as the symbol for the color randomization to work properly.
The Projection tab is used to reinterpret the raw vector data to a new projection. This is useful if the wrong projection was selected for the dataset when it was loaded, or if the data set itself indicated some incorrect data. This option is rarely used. You can however also use the Elevation Units control to specify what elevation units that values in the vector data that do not explicitly specify their units should use. This is useful to indicate if the values associated with 3D vector features or with the ELEVATION attribute for features are in feet or meters.
Raster Data Options
Selecting the Options... button while only raster overlays are selected displays the Raster Options dialog. The Raster Options dialog consists of several tabs, each allowing you to control various aspects of how the selected raster layers are displayed.
The Display tab (pictured below) contains controls allowing you to control the color intensity (brightness/darkness), color transparency, blending, anti-aliasing, and texture mapping of the selected layers.
The Color Intensity setting controls whether displayed pixels are lightened or darkened before being displayed. It may be useful to lighten or darken raster overlays in order to see overlaying vector data clearly.
The Translucency setting controls to what degree you can see through the overlay to overlays underneath the overlay. The default setting of Opaque means that you cannot see through the overlay at all. Settings closer to Transparent make the overlay increasingly more see-through, allowing you to blend overlapping data.
The Blend Mode setting controls how an overlay is blended with underlying overlays, in addition to the Translucency setting. These settings allow Photoshop-style filters to be applied to overlays, resulting in often stunning results. What you get from a particular set of overlays from a particular blend mode setting can often be hard to predict, so rather than try to understand what is technically happening for each blend mode it's best to just experiment with different ones until you find one that you like. The Hard Light setting seems to work well with satellite imagery overlaid on DEMs, but the others can be quite useful as well. For example, the Apply Color setting is useful for applying color to a grayscale overlay, such as using a low-resolution color LANDSAT image to colorize a high-resolution grayscale satellite image. The SPOT Natural Color blend mode combines the color channels in the topmost layer using the common algorithm for generating natural color imagery from images from the SPOT HRV multi-spectral sensor [Red = B2; Green = ( 3 * B1 + B3 ) / 4; Blue = ( 3 * B1 - B3 ) / 4]. The Pseudo Natural Color blend mode combines the color channels within a single image using a common algorithm for generating natural color imagery from CIR imagery. The Color to Grayscale blend mode converts a color image to grayscale.
The Transparent option allows a particular color (or colors) to be displayed transparently, making it possible to see through a layer to the layers underneath. For example, when viewing a DRG on top of a DOQ, making the white in the DRG transparent makes it possible to see much of the DOQ underneath. Pressing the Set Transparent Color... button allows the user to select the color (or multiple colors for palette-based files) to treat as transparent in the selected overlay(s) as well as save the palette for palette-based files to a color palette (.pal) file. If you also check the Make Very Similar Colors Transparent as Well option, any colors that are a very similar color to the selected transparent color will also be displayed transparently. This is useful for getting rid of colors in lossy formats like JPG and ECW where the colors are not exact.
The Resampling option allows you to control how the color value for each displayed/export location is determined based on the values in the file. The following resampling methods are supported:
- Nearest Neighbor - simply uses the value of the sample/pixel that a sample location is in. When resampling or reprojected an image this can result in a stair-step effect, but will maintain exactly the original color values of the source image.
- Bilinear Interpolation - determines the value of a new pixel based on a weighted average of the 4 pixels in the nearest 2 x 2 neighborhood of the pixel in the original image. The averaging has an anti-aliasing effect and therefore produces relatively smooth edges with hardly any jaggies.
- Bicubic Interpolation - a more sophisticated method that produces smoother edges than bilinear interpolation. Here, a new pixel is a bicubic function using 16 pixels in the nearest 4 x 4 neighborhood of the pixel in the original image. This is the method most commonly used by image editing software, printer drivers and many digital cameras for resampling images.
- Box Average (3x3, 4x4, 5x5, and 7x7) - the box average methods simply find the average values of the nearest 9 (for 3x3), 16 (for 4x4), 25 (for 5x5), or 49 (for 7x7) pixels and use that as the value of the sample location. These methods are very good for resampling data at lower resolutions. The lower the resolution of your export is as compared to the original, the larger "box" size you should use.
- Box Maximum (3x3, 4x4, and 5x5) - the box maximum methods simply find the maximum value of the nearest 9 (for 3x3), 16 (for 4x4), 25 (for 5x5), or 49 (for 7x7) pixels and use that as the value of the sample location. These methods are very good for resampling elevation data at lower resolutions so that your new terrain surface has the maximum elevation value rather than the average (good for terrain avoidance). This method behaves the same as the average on raster/imagery layers. The lower the resolution of your export is as compared to the original, the larger "box" size you should use.
The Texture Map option allows a 2D raster overlay to be draped over loaded 3D elevation overlays. Selecting the check box causes the overlay to use any available data from underlying elevation layers to determine how to color the DRG or DOQ. The result is a shaded relief map.
Color/Contrast Adjustment Tab
The Color/Contrast Adjustment tab (pictured below) allows you to control the color balance and contrast of the selected overlay(s).
The Color Balance sliders allow you modify the relative amounts of red, green, and blue in the image, thus allowing precise control over the color balance in the image.
The Contrast Adjustment options are used to adjust the contrast of imagery. The Linear (Percentage Stretch) contrast adjustment method applies a standard deviation contrast adjust to each color channel in the image. You can specify how many standard deviations from the mean that the range is stretch to for rendering, although you'll generally want to stick with the default of 2. This is particularly useful for improving the display of dark or satellite imagery, such as IKONOS images, and is required for the display of imagery with more than 8 bits per color channe. The Linear (Min/Max Stretch) method finds the minimum and maximum values in each color channel and stretches that range to a range of 0 to 255. For most imagery with 8 bits or less per color channel this will have no effect, but can produce a good result for high-color imagery.
The Share Contrast Adjustment with Other Layers checkbox allows you to specify that the calculated contrast adjustment used should be based on all loaded raster layers that have contrast adjustment enabled rather than just the color histogram for this single layer. This is enabled by default and provides consistent results when adjusting the contrast for multiple mosaiced images.
The Cropping tab (pictured below) allows you to crop the selected overlay(s) to a particular boundary, including support for automatically removing the collars from USGS DRG topographic maps.
The Automatically Crop Collar (DRG/BSB/etc.) option is used to automatically remove the collar from loaded raster data if the collar is in a recognized format. Most frequently it is used to removes the white border around a DRG, the small black collar around a 3.75 minute DOQQ, or the map collar around a BSB marine chart. This allows you to seamlessly view a collection of adjacent BSB, DRG, or DOQQ files.
The Crop to Manually Specified Lat/Lon Boundary option allows you to specify a lat/lon boundary (in the native datum of the selected overlay) to crop the overlay to. When selected, this option will display the Customize Collar Bounds dialog (pictured below) to allow specifying the bounds to crop to.
The Crop to Manually Specified Boundary in Native Layer Projection/Units option allows you to specify a crop boundary in the native units of the selected overlay. When selected, this option will display the Customize Collar Bounds dialog (pictured above) to allow specifying the bounds to crop to.
The Crop a Specified Number of Pixels Around the Edges of the Layer option allows you to specify a number of pixels to crop of each edge of the selected overlay(s).
The Snap to Manually Specified Degree Boundary option allows you to specify that the collar for the selected overlay will be on some degree boundary, like an even degree, of 0.5 degrees, etc. This way you can setup cropping for a collection of maps that are all similarly aligned.
The Crop to Previously Selected Polygon(s) option specifies that you want to crop to the crop polygon(s) (area) previously applied to the selected layer(s) using the Crop to Currently Selected Polygon option.
The Crop to Currently Selected Polygon(s) option specifies that you want to crop the selected layer(s) to any area feature(s) currently selected with either the Feature Info or Digitizer Tools.
Band Setup Tab
The Band Setup tab (pictured below) is available for some types of imagery with 3 or more bands of data. This tab allows you to control which bands of data are used for the red, green, and blue color bands. This is a very useful tool when trying to extract different types of information out of multi-spectral imagery.
There is also an option for advanced users to allow disabling of the alpha (translucency) channel for an image. This is useful if you have an image with bad alpha values (like all set to completely transparent) and you just want to see the colors without applying the alpha values.
The Palette tab (pictured below) is available for raster image files that use a fixed color palette for display. This tab allows you to see what colors are in the palette as well as edit the color and/or description of each color in the palette. This allows you to easily replace one color with another. You can also save the palette to a new file or load an entirely new palette to use for the layer from an existing .PAL or .CLR file.
The Feathering tab (pictured below) allows you specify that you would like to feather-blend the selected overlay(s) with the underlying overlay(s) on the specified edges. This can be extremely powerful tool for blending imagery/maps from different sources and/or at different resolution to make the edge between the map sets invisible. You can choose to either feather-blend around the edges of selected files or along the boundary of one or more selected polygons. Feather blending can be used on both raster (imagery) layers as well as gridded elevation layers. In the case of elevation layers, the feather blending works by calculating modified elevation values based on elevation value in the blended layer and the topmost elevation layer underneath the blended layer in the draw order.
The screenshot below displays the results of feather-blending a very high resolution data set (0.15 meters per pixel) with a lower resolution (3.5 meters per pixel) dataset to remove the edge. Note that the higher resolution image has been purposely tinted violet to make the effect more obvious.
Color Grade Tab
The Color Grade tab (pictured below) allows you to apply complex color correction to a loaded raster file. You can setup the input range for each color channel and what output range to map it to, as well as specify a saturation value.
Elevation Data Options
Selecting the Options... button while only gridded elevation overlays are selected displays the Elevation Options dialog. The Elevation Options dialog consists of two tabs, one for controlling the display of the overlay(s) and the other for modifying the elevation values within the overlay(s).
The Display tab (pictured below) contains controls allowing you to control the color intensity (brightness/darkness), color transparency, blending, anti-aliasing, and color shading of the selected layers.
The Color Intensity setting controls whether displayed pixels are lightened or darkened before being displayed. It may be useful to lighten or darken raster overlays in order to see overlaying vector data clearly.
The Translucency setting controls to what degree you can see through the overlay to overlays underneat the overlay. The default setting of Opaque means that you cannot see through the overlay at all. Settings closer to Transparent make the overlay increasingly more see-through, allowing you to blend overlapping data.
The Blend Mode setting controls how an overlay is blended with underlying overlays, in addition to the Translucency setting. These settings allow Photoshop-style filters to be applied to overlays, resulting in often stunning results. What you get from a particular set of overlays from a particular blend mode setting can often be hard to predict, so rather than try to understand what is technically happening for each blend mode it's best to just experiment with different ones until you find one that you like. The Hard Light setting seems to work well with satellite imagery overlaid on DEMs, but the others can be quite useful as well.
The Transparent option allows a particular color to be displayed transparently, making it possible to see through a layer to the layers underneath. For example, when viewing a DRG on top of a DOQ, making the white in the DRG transparent makes it possible to see much of the DOQ underneath. Pressing the Set Transparent Color... button allows the user to select the color to treat as transparent in the selected overlay.
The Resampling option allows you to control how the elevation value for each displayed/export location is determined based on the values in the file. The following resampling methods are supported:
The Shader option allows you to choose which elevation shader is to be used for coloring the cell values within this layer. By default, all gridded layers will share the elevation shader selected on the toolbar, but there may be certain situations where you want to color one layer differently than the others and exclude it from the loaded elevation range. One common example is a gridded layer that actually has non-elevation data.
The Alter Elevation Values tab (pictured below) allows you to modify how elevation values from the selected layer(s) are interpreted, providing you a means to offset all of the elevations in the layer(s) by a given value and to restrict the range of elevation values that are treated as valid.
Toggles whether the currently selected overlays are visible. You can also use the checkboxes next to each layer to control the visible state of the overlays.
Closes all the currently selected overlays.