Using Elevation Data

Introduction

Sooner or later during the tour planning it is interesting to have a look at the elevation profile of your tour - just to not face bad surprises during the trip. FancyRoute offers tools in order to inspect and assess elevation profiles.

In case the tour is supplied by a third party the necessary elevation data might already be part of the track. For others maybe not.

FancyRoute can help with functions to add elevation data to the tour.

Configuration

First some settings have to be arranged, proceed to ‘Menu-Options-Preferences-Elevation’.

image_prefs

Note: The data source “U.S. Geological Survey (usgs.gov, 3DEP 10m) - US area” is not accessible using Windows 7 or older due to unsupported encryption ciphers.

Set the Elevation Data Source

Most of the maps do not contain elevation information. FancyRoute has to get it from additional sources. Group ‘Elevation data source’ lets you determine such sources.

FancyRoute is designed for offline usage. So the recommended way to retrieve data is to let FancyRoute try offline sources first and probably fall back to online sources then.

Multiple sources can be enabled. FancyRoute accesses them on demand, trying one source after another until the data is complete. Not all sources cover the entire world necessarily.

The source order can be arranged using the up/down buttons whereas the checkbox enables/disables the source.

Use the test button in order to proof a certain data source.

Offline Elevation Sources

Offline sources (elevation data installed on a local disk) have the charming advantage to be available at any time, anywhere and without delay. FancyRoute can seamlessly work with this data in order to show the current elevation under the moving cursor in the map. It can show the elevation of a route or track in a diagram without having to obtain the elevation explicitly.

Offline elevation sources makes the work much more efficient and independent.

Tip: It is recommended to exclude the locally installed elevation sources from virus scan. FancyRoute heavily accesses these files during operation. Not scanning the elevation data improves the performance dramatically.

Top50 offline data

The TOP50 series (commercial product on CD/DVD by the German and Austrian Landesvermessungsämter) contains an excellent digital ground model (DGM) for Germany, Austria and Switzerland. FancyRoute can use it as elevation source.

Enable this source if Top50 is available. Make sure the right base folder is set in ‘Menu-Options-Preferences-Raster Map’, group ‘General’.

SRTM offline data

SRTM is the Shuttle Radar Topography Missions. Its data is publicly available as HGT formatted data, see APPENDIX A. SRTM1 provides data with a 30m resolution whereas the SRTM3 data have a 90m resolution.

The complete SRTM3 database (75GB cover the entire globe) can easily be installed on a travel notebook in order to be independent. The data have a long life cycle, it is worth the one-time installation effort.

Enable one of these sources, then set the corresponding path in ‘Database folders’. For details see APPENDIX-A, chapter How FancyRoute expects HGT files.

Online Elevation Sources

Online sources offer online access to elevation data on demand. Internet access is required here. Sometimes it is desired to just have the option to retrieve the elevation profile of a route on a system not having offline data present.

Online sources make your work dependent from the generosity of public servers that are often throttled in reality and sometimes require an account, even though the account is free of charge.

Enable these sources as backup to the offline sources described in the chapter above.

For the GeoNames server don’t forget to insert the user name of your account to the related field at the bottom end of the setup dialog.

Elevation Diagram

The elevation diagram shows the elevation profile of a route or track.

Select a route or track, then use ‘Menu-View-Toolbars-Elevation’.

image_diagram

If the route/track already contains elevation data the elevation profile is displayed immediately, otherwise the graph shows a flat line. Use the buttons in the bottom right corner to make a forecast in this case.

Button Remarks
image_btn1 Makes an elevation forecast. If the configuration misses a valid offline source this button disappears.
image_btn2 Smooths the curve.
image_btn3 Shows the gradient curve.
image_btn4 Shows the accumulated elevation gain.

Use the sliders to zoom in/out. Click into the graph area to synchronize with the map.

The diagram shows waypoints along the way as green marks. This option can be set in ‘Menu-Options-Preferences-Diagrams’, group ‘Elevation diagram’.

Add Elevation Data to a Course

In order to enhance a route or track or even a waypoint with elevation data select the item, then apply ‘Menu-Project-Obtain Elevation Data’.

This function is grayed out if the configuration doesn’t specify valid elevation data sources.

Tip: If the elevation information of a track is incomplete (some points missing) then obtain the elevation data for these points selectively:

  • Proceed to the waypoints pane.
  • Make sure the column ‘Elevation’ is visible.
  • Hold SHIFT pressed and click the ‘Elevation’ column header to select all empty points.
  • Apply ‘Menu-Project-Obtain Elevation Data’.

Work with Gradient Histograms

The gradient histograms shows how much of the course is steep or rather flat. Use it in order to assess the training intensity of a course.

image_hist

In the example above the center bar shows that 4.5km of the entire course has a gradient between -2.5% and +2.5%. So a good third of the course is rather flat.

The short bar above (0.5km length) covers slopes between 2.5% and 6%. This is not steep but makes you sweat on the bike.

The bar above, ca. 0.7km length covers parts that are really steep slopes between 6% and 12%. This is what you can still do for a while as a trained biker.

The top bar shows the parts above 12%. In this example the slopes above 12% sum up to a distance of 3km - normal for hiking, challenging on the bike.

The bars below the center bar show descending parts of the course.

The histograms can be configured in ‘Menu-Options-Preferences-Diagrams’, group ‘Histogram increments’.

APPENDIX A

HGT files serve as local, offline database for elevation data used by FancyRoute. This section gives insights into HGT files and their usage.

How FancyRoute expects HGT files

‘Menu-Options-Preferences-Elevation’, group ‘Database folders’ offers two fields for setting the path to SRTM1 or SRTM3 data. If SRTM1 or SRTM3 is selected as elevation data source the corresponding path to the HGT files have to be set. The path has to contain the HGT files - unzipped, without sub-folders, all files ending .hgt.

Sources for HGT Data Download

An excellent source for HGT data is http://viewfinderpanoramas.org/dem3.html.

For SRTM3 data (3 arc-seconds, 90m resolution) proceed to Download data: 3”, select the wanted region and unpack the HGT-files into a folder like described in the chapter above. The SRTM1 data (1 arc-second, 30m resolution) select 1”.

Another source for HGT data is https://wiki.openstreetmap.org/wiki/SRTM.

Make sure it is data from the right mission (SRTM1 or SRTM3) you download (see next chapter).

HGT File Structure

The HGT file can be considered as grid data containing elevation values of a certain area of the globe. Elevation values are arranged in rows and columns.

SRTM1

Each SRTM1 HGT file covers an area of 1° latitude and 1° longitude with a resolution of 1 arc-second. So it contains 3601 lines (1° == 3600 arc-seconds == 3600 samples to 1 arc-seconds + 1 overlap sample) and the same amount of columns. Each file contains exactly 3601x3601x2=25934402 bytes.

Each elevation sample is represented by a 2 byte value in big-endian format, encoded as integer value in two’s complement. A value of -32768 is reserved for invalid data.

SRTM3

Each SRTM3 HGT file covers an area of 1° latitude and 1° longitude with a resolution of 3 arc-seconds. So it contains 1201 lines (1° == 3600 arc-seconds == 1200 samples to 3 arc-seconds + 1 overlap sample) and the same amount of columns. Each file contains exactly 1201x1201x2=2884802 bytes.

Each elevation sample is represented by a 2 byte value in big-endian format, encoded as integer value in two’s complement. A value of -32768 is reserved for invalid data.