Viewing and Inspecting Rasters

Liz Sanderson
Liz Sanderson
  • Updated

FME Version

  • FME 2023.2

Introduction

Raster data comes in two types, color rasters and numeric rasters. In this article, we will inspect both a color raster, in this case, an orthophoto GeoTIFF, and a numeric raster, which will be a digital elevation model.

Please keep in mind that FME Data Inspector is only able to view your data. It cannot perform any transformations or translations to the data.

 

Video

See how you can view RGB and DEM rasters in the FME Data Inspector. This video demonstrates GeoTIFF and CDED formats. Clicking a cell shows the pixel row and column, ground location, and RGB / RGBA bands (color values) or DEM value (elevation data). Selecting the entire raster shows the coordinate system info, format-specific attributes, extents, resolution, origin, information about each band, and other metadata.
 

Step-by-Step Instructions

Part 1: Viewing and Inspecting an RGB Raster

1. Start the FME Data Inspector

Start the FME Data Inspector by clicking on the program icon with the bulls-eye and the accompanying circle below it.

FME Data Inspector

Note: The data used in this section is available in the files section of this article.

2. Open the Dataset

Click on the Open a dataset in a new view tool (folder icon) in the upper left corner. For Format, type in GeoTIFF and select GeoTIFF (Geo-referenced Tagged Image File Format). For Dataset, click on the ellipse (3 dots) and browse to 06-07-NO.tif; click OK to add the data. This GeoTIFF file is an orthophoto tile of Coal Harbour in downtown Vancouver, British Columbia.

data-window.png

 

Once the data is read in, notice the “(1)” next to the feature type in the Display Control pane. This confirms that FME reads a raster as one feature.

view-geotiff1.png

 

3. Query Information About a Single Cell

By default, your mouse is set to the Select and Information tool. Click anywhere on the raster to query a cell. Once a cell has been clicked on, information about that cell appears in the Feature Information pane. There is information about the row and column, ground location information, raster colors and band values.

06-tiff-data-inspector.png

 

4. Query Information for the Entire Raster

To select the entire raster, click anywhere outside of the raster, then click and hold your mouse (left button) and drag it into the raster; a blue box should appear. You will know the entire raster is selected when a grid of dots appears over the entire image.

Using this method, the entire raster is selected instead of an individual cell, and the Feature Information window gives us property details for the entire raster. We have coordinate system information, GeoTIFF-specific attributes, extents, resolution, origin, and specifics about each band.

06-tiff-data-inspector-whole-raster.png

 

Part 2: Viewing and Inspecting a DEM Raster

1. Open the DEM-Clipped.dem File

In the Data Inspector, click the Open a dataset in a new view tool to view the digital elevation model (DEM). For Format type CDED and select the Canadian Digital Elevation Data (CDED) format. Then browse to DEM-Clipped.dem for the dataset. Click OK to view the data.

data-window-dem.png

2. Query Information About a Single Cell

In a numeric raster, each cell contains a numeric value for the specific geographic area covered by that cell. In this case, the numeric value of each cell represents an elevation value. Click on various parts of the image to see how the elevation changes from black to light gray. Numeric raster - In the Feature information window, the 'Band 0 (INT32)' value is the elevation value of the point selected.

DEM-cad-1.png

3. Query the Entire Raster

Using the technique mentioned in the previous example, select the entire raster. In the Feature Information pane, there will be information about the coordinate system, extents, origin, cell spacing, resolution, the number of bands, and information about the bands.

DEM-entire-1.png

 

Data Attribution

The data used here originates from open data made available by the City of Vancouver, British Columbia. It contains information licensed under the Open Government License - British Columbia.

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