Viewing and Inspecting Rasters

Introduction

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

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

The data used in this step-by-step tutorial is available in the Files section of this article.

Video

This video was filmed using FME Data Inspector 2016; although the interface may look different, the concepts are still the same. 

Step-by-Step Instructions

In this tutorial, you'll learn how to view and inspect rasters in FME Data Inspector.

Part 1: Viewing and Inspecting an RGB Raster

In this first part of the tutorial, you'll learn how to view and inspect raster information in FME Data Inspector. We will be using a GeoTIFF raster.

1. Start FME Data Inspector

Start FME Data Inspector (program icon shown below).

2. Open the Dataset

Click on Open Dataset in the Get Started pane or Open (folder icon) in the upper left corner of the menubar. Type "GeoTIFF" in the dialog and select GeoTIFF (Geo-referenced Tagged Image File Format) for the Format parameter. For the Dataset parameter, click on the ellipse (...) 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.

Once the data is read in, notice the View 1 (1) under the Display Control pane. This confirms that FME reads a raster as one feature.

3. Query Information About a Single Cell

Your mouse is set to the Select and Information tool by default. 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. This includes the row and column, ground location information, raster colors, and band values.

4. Query Information for the Entire Raster

To select the entire raster, click anywhere outside of it, then click and hold your mouse (left button) and drag it into the raster; a blue box should appear while you do this. You will know the entire raster is selected when a colored outline appears around the whole image (shown in the image below).

Using this method, the entire raster is selected instead of an individual cell, and the Feature Information window updates to give us property details for the entire raster. We have a coordinate system and GeoTIFF-specific attributes, extents, resolutions, origins, and specifics for each band.

Part 2: Viewing and Inspecting a DEM Raster

In this second part of the tutorial, you'll learn how to view and inspect raster information in FME Data Inspector. We will be using a DEM raster.

1. Open the DEM-Clipped.dem File

In FME Data Inspector, click the Open Dataset in the Get Started pane or Open (folder icon) in the upper left corner of the menubar. Type "CDED" in the dialog and select Canadian Digital Elevation Data (CDED) for the Format parameter. For the Dataset parameter, browse to DEM-Clipped.dem. Click OK to add the data.

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.

The Band 0 (INT32) property in the Feature Information window shows the elevation value.

3. Query the Entire Raster

To select the entire raster, click anywhere outside of it, then click and hold your mouse (left button) and drag it into the raster; a blue box should appear while you do this. You will know the entire raster is selected when a colored outline appears around the whole image (shown in the image below).

The Feature Information pane will contain information about the coordinate system, extents, origin, cell spacing, resolution, the number of bands, and information about the bands.

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 - Vancouver.