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Managing Map Layers

 

This section describes the layer types that are supported in the Map Viewer and how to manage them.

 

Supported layer types

The following types of layers are supported file types are supported in the Map Viewer maps:

 

 

Vector Data

Vector datasets represent discrete locations as one or more points, polylines, or polygons. Each point, polyline, or polygon is composed of spatial information (i.e the set of vertices that define the point, polyline, or polygon) and associated attributes (i.e. information about the point, polyline, or polygon).  There are two types of supported vector datasets in Hydro GeoAnalyst 12.0:

 

Hydro GeoAnalyst Data (Project Data-Driven Layers):

Project Data-Driven Layers are point locations with associated data that are dynamically generated by Hydro GeoAnalyst based on data in the the project database:

Spatial Queries from the project tree that include the X and Y location fields from the station "Location" table

 

Station Groups from the project tree as defined in the station list (static groups) or in the query builder (dynamic sets)

 

Sample Sets from the project tree as  defined in the sample list (static sets) or query builder (dynamic sets) [HGA+ only]]

 

Shapefiles

Shapefiles are an open source vector-based Geographic Information Systems (GIS) data format developed by ESRI (1998) that includes a set of points, polylines, or polygons.  Shapefiles can be loaded into HGA and consist of a set of files with the same base file name — four of these are required for use in the Map Viewer Module: .shp (spatial data), .shx (spatial index), .dbf (attribute data), and .prj (coordinate reference definition).  Shapefiles can be imported from external sources in Hydro GeoAnalyst.

 

Raster Datasets

Raster datasets generally represent continuous data over a specified area discretized in a grid of point values.  There are two main types of raster datasets supported in the Map Viewer:

 

Image formats

Images are a grid based data type covering a defined rectangular area and are commonly used to store/present basemaps and aerial imagery.  Hydro GeoAnalyst supports common image types (.bmp, gif, .png, .tif) with an associated world file.

 

Surfaces

Surfaces are a grid-based data type that covers a defined area with each point on the grid representing values of some generally continuous dataset (e.g. elevation, concentration, temperature, etc.). <%APP> supports two of the most common raster surface formats, Surfer Grid Files (.grd) and ESRI ASCII Grid Files (.asc). Surfaces can also be created by interpolating data from a project data-driven layer (i.e. a spatial query, a station group, or a sample set)

 

Please Note: the projection of the image or surface must match that of the map. On-the-fly Image reprojection is not currently supported in Hydro GeoAnalyst 12.0.

 

Adding a map layer

You can add a layer to the map by:

Clicking the Add layer button [] in the map layers toolbar to open the Add map layer dialog

Dragging-and dropping a station group, sample set, or Spatial Query onto the Layer Tree or Map Viewport

Dragging-and-dropping a supported external file type (shapefile, image, or surface) from a Windows Explorer window onto the Layer Tree or Map Viewport

 

Add Map Layer Window

The Add Map Layer window includes a radio button selection for the type of layer to add:

 

Add Station Group/Sample Set

Selecting the station group or sample set option shows a searchable subset of the project tree that includes the station groups and sample sets:

 

Note: Sample Sets are only available in HGA+

 

Clicking the button adds the selected station group or sample set to the layer tree and map viewport.

 

Add Query

Selecting the station group or sample set option shows a searchable subset

 

Add Shapefile

Selecting the Shapefile option and clicking the button opens the windows explorer and allows you to navigate to and select a shapefile to be added to the layer tree and map viewport.

 

Add Image

Selecting the Image option and clicking the button opens the windows explorer and allows you to navigate to and select an image file (.bmp, .jpg, .png, or .tif) to be added to the layer tree and map viewport. A valid world file, must also be present to georeference the image.

 

Add Surface

Selecting the Surface option and clicking the button opens the windows explorer and allows you to navigate to and select a surface file (.grd or .asc) to be added to the layer tree and map viewport.

 

Add Cross Sections

Selecting the Cross sections option and clicking the button adds all cross sections in the project as a single polyline layer to the layer tree and map viewport.

 

Working with Map Layers

You can toggle the visibility (show/hide) a layer on the map by toggling the layer checkbox in the Map Layers tree.

You can reorder the layers by clicking, dragging, and dropping the selected layer in the desired position on the map. Layers at the bottom of the tree are rendered first so that they appear "under" layers higher up in the tree.

 

Deleting a Map Layer

To delete a layer from the map, simply select it in the Map Layers tree and click the delete layer [] button to remove it from the Map.

 

Exporting Map Layers

To export a map layer, select it in the map tree and select the Export Shapefile button in the Map Layers toolbar. The subsequent export steps depend on the type of layer to be exported as follows:

 

If the selected layer is a Point Layer whether from an external shapefile, station group, sample set, or spatial query, then you will be prompted to select the export file path and you will have the option to add a numerical field as the Z-coordinate:

 

If the selected layer is a Polyline or Polygon layer, then you will be prompted to select an export file path

 

If the selected layer is a surface, then you will be prompted to save one or more types of information:

 

oExport grid points: exports a point shapefile with one point at the centroid of each grid cell including the elevation (or surface value).

oExport major contour lines: exports a polyline shapefile with the major contour lines currently displayed on the map

oExport minor contour lines: exports a polyline shapefile with the minor contour lines currently displayed on the map

 

Images and Surfaces cannot be exported to a shapefile

 

 


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