Infos pratiques

WindMap© version 1.06- released 01.04.2010

Dr. Beda Sigrist, the author of TherMap, has produced these maps intended to show the effect of ridge winds. Their utilization for non-commercial purposes is free. For commercial uses, quotations, as well for further publication written permission must be obtained via the mail address mentioned at the end of this site, and this site quoted as the source.

Ridge Wind Maps

A complement to TherMap

Français - Deutsch

Welcome to WindMap

During the last years long distance mountain flights have demonstrated the longtimes underestimated potential of ridge winds. Due to this, and following the positive experiences with TherMap, the meteorological section of OSTIV also expressed an interest in ridge wind maps. WindMap is attempting to provide an answer to this.

Position the cursor on the picture on the left and you can see a map extract of WindMap, a tool for glider pilots, to visualize the local potential of ridge winds for a given wind direction, assuming no other meteorological interferences or mountain waves. The WindMap picture also contains an actual flight track showing the flight phases with climbing (blue) and sinking (white) phases.

For every multiple of 15 degrees (e.g. wind from 195° in the case of the sample), ridge wind maps may be downloaded from this site. As an alternative, a CD containing a complete set of the maps for Switzerland, Austria, the French Alps, the Pyrenees as well as the Northern and Central Apennine can be ordered at a cost covering charge.

Before the flights WindMap allows you to study the best itineraries, or to explain them to less experienced pilots, particularly across less known regions. After the flight, you may superimpose your flight tracks on these maps, typically IGC-files, to find out where you might have followed more promising paths. The maps may also be imported as raster maps into certain flight analysis applications.

What is new in WindMap 1.06 ?
On the new download maps slopes facing the wind are hatched if they are likely to be in the windshade of the upwind terrain, a risk which can easily be underestimated. In addition, on the underlying topographic maps, surfaces which are practically flat are shown in very light colours, in order to better mark minor edges of the terrain. To facilitate the reading texts and gridlines are now displayed in combined black and white. The colouring of the upwind areas has however remained unchanged, having found no valid alternatives despite intensive research. An important extension is however the new possibility to automatically overlay the maps on Google Earth, where they can be visualized as 3D-displays as well as in 3D flight simulations.

The consideration of large scale wind channeling effects remains an area of interest, but this should be treated as a separate project. Otherwise this might impair the easy interpretation of the present maps.


The Model Using the maps Downloads View in
Google Earth
Order CD FAQ Links Contact


The Model a. Simple ridge wind maps
b. Maps considering channelled ridge wind

a. Simple ridge wind maps

Digital elevation models (DEM), such as the worldwide 90m SRTM satellite models, provide a relatively detailed topological profile of the surface of the earth. Extracts of these files can be used to determine the special orientation of each surface cell of about 90 meters. If wind from a given direction blows against such a surface field, it will usually be diverted by the latter, basically in the direction of the intersection between the plane of the surface field and the plane determined by the original wind vector and its mirror on the surface plane. This is of course only applicable where the wind vector meets a surface element from above. The vertical component of the diverted wind is used as a measure of the upwind potential at the location of each surface field. A further factor of importance is the downwind area behind obstacles within which no upwinds can be expected. Based on empirical analyses WindMap assumes these areas to be determined by a shadow declining by 10 degrees in the direction of the wind. Despite its simplicity this model already leads to fairly realistic ridge wind maps, as illustrated on the sample map shown below.

b. Maps considering channelled ridge winds

In the simple model the wind deflection is calculated independently for each surface element. In practice this is only partly valid, namely when adjacent surface elements have the same spacial orientation. However if wind blows up a narrowing valley, the air flow tends to be compressed and hence the wind normally accelerated. In the present, refined model, such compression effects have been considered over a local distance of about 400 meters. This has led to more pronounced maps, as can be seen when moving the cursor over the picture of the simple model below. The refined method has therefore been used for all maps offered on this site..

Region east of lake Walensee, for wind from 195°, generated by the simple model.
Moving the cursor over the picture reveals the refined map with channelled ridge winds.

Using the maps

a. Selecting the right maps
b. Limitations of the WindMap approach
c. How to read the maps
d. Preflight use of maps
e. Post-flight analysis using the maps

a. Selecting the right maps

Land :

Depending on the extent of your flight you may have to select the maps of more than one country or region

Country/Region North-West Corner South-East Corner
Switzerland 48° 00'’ N / 05° 30’ E 45° 30'’ N / 11° 00’ E
Austria 48° 00'’ N / 09° 30’ E 46° 00'’ N / 16° 20’ E
French Alps 47° 30'’ N / 05° 00’ E 43° 00'’ N / 07° 30’ E
Pyrenees 43° 20'’ N / 03° 00’ W 42° 00'’ N / 02° 30’ E
North Apennine 45° 00'’ N / 07° 30’ E 43° 30'’ N / 12° 30’ E
Central Apennine 43° 30'’ N / 11° 30’ E 41° 00'’ N / 15° 00’ E

Wind direction : WindMap offers 24 maps per region, with 15° increments for the wind directions from 15° to 360°. Select the maps showing the main wind directions of your flight. The wind directions are included in the file name.

b. Limitations of the WindMap approach

  • Limitations of radar maps: Radar reflection signals are not perfectly precise when scanning altitudes. They are rather unreliable when reflected by water or ice. This it why it is difficult to automatically identify lakes on the basis of radar scan data. In the present TherMap version many lake outlines have therefore been imported separately, but these imports had to be limited, due to the manual effort involved, and hence not all lakes are displayed. Ice covered surfaces may appear blurred. Fortunately neither of these limitations is of real importance for the use of the TherMap maps.
  • Changing wind direction: WindMap is based on a simple local model and each map is calculated for one single wind direction. Wind directions and strength can however change with the altitude and the geographical position. This can lead to atmospheric interactions not covered by the WindMap model and which the users must therefore interpret accordingly.
  • Other influences: Whilst one part of a distance flight may be determined by ridge winds another part may be dominated by thermals, with a blurred transition zone in between. In such cases it is advisable to study the corresponding maps for both, WindMap and TherMap. On the other hand during days with strong winds it is possible to meet upwinds at locations having no potential according to WindMap. This can be due to mountain waves or large scale channelling effects, none of which are considered in the WindMap model..

c. How to read the maps

  • Zooming: The maps should be zoomed at least to 100 percent. Original maps may contain around 20 megapixels, which corresponds to about 25 standard screens. The maps are worthwhile to be studied in detail, if necessary by zooming above 100 percent, due to their huge information content. For your convenience it is recommended to use viewers (e.g. MS Picture Manager®) permitting to maintain the zooming level and the selected window frame while paging between different images.
  • Colour coding: As a backdrop WindMap uses simple topographic maps illuminated more realistically from South-West. A basic wind speed of 6 m/sec has been assumed. Its vertical component must reach at least 25 percent of this, i.e. 1.5 m/sec, allowing a glider with a sinking speed of 0.75 m/sec to climb at about the same rate. Above this level the maps are coloured as follows: Zones with a moderate climbing potential are coloured from dark to light red (net climbing rates of 0.75 to 1.75 m/sec), whilst regions above this are coloured from beige to yellow. This is illustrated by the following colour diagram:

    At regular intervals the maps show white lines in the direction of the wind . These lines only appear in downwind areas where no updrafts are expected. Slopes facing the wind are hatched if they are expected to be in the windshade of upwind terrains.

  • 3D visualisation: Importing the corresponding TherMap maps into Google Earth® (KML Ground Overlays) or SeeYou® (raster maps) takes a few minutes, but this can facilitate the preparation or the retrospective analysis of flights, particularly when using the 3D mode. The advantage of Google Earth is that "flight" routes can be freely chosen, which is useful for flight preparations. For flight analyses the IGC records are frequently extracted via SeeYou, but can easily be converted to KML-format of Google Earth, which does not require importing the maps, but offers less possibilities for illustrating the flight path.

South foehn near Innsbruck, Austria: WindMap 3D-view für 195° wind, with Variometer flighttrack (reproduced with SeeYou©)

d. Preflight and in-flight use of maps

  • Meteorology: Meteorological wind maps show that wind direction and strength change with time, location, and altitude. WindMap shows a different map for each wind direction and its use is only indicated if ridge winds predominate thermal updrafts. This depends on the careful judgement of the user. Under these conditions the maps of WindMap can be a useful complementary tool to the meteorological forecasts.
  • Pre-checking planned flight paths: WindMap is best used before the flight to check ridge wind situations at the expected time of overflight.
  • In-flight use of WindMap: Consulting a map printout during the flight must not interfere with the necessary observation of the flight space. Tests with mobile navigation tools, into which TherMap hotspots had been imported, have shown that distraction from flight observation remains an issue, besides the poor readability of most navigation devices. Future devices may one day offer better readability. However even then, the mobile tools should be designed to automatically show the hotspots depending on the actual wind direction at a given location, to avoid distracting the pilot when manually loading of the correct map file.

e. Post-flight analysis using the maps

  • The wind direction of the maps used must be the same as that of the flight segment investigated. Digital flightlogs provided by IGC-files are very precise and may therefore permit to identify more easily where better itineraries might have been followed. In order to minimize their size, TherMap files are in JPG format.
  • As already mentioned, solution providers like GoogleEarth ® and SeeYou® offer functions to import WindMap files and to view them from above or in 3D. Goggle does not need to convert the files into another format. Where possible, it is also recommended to show the flight path in variometer option, in order to visualize the climbing and sinking phases of the flight. When importing the raster maps you have to enter the positions of the country maps used (NW and SE corner coordinates), as indicated under section a.

Example with foehn blowing from the South near Innsbruck. For better contrast flight phases with significant ridge winds are shown in blue.
This map has been produced with WindMap.


Select for the desired country region (Switzerland, French Alps, Austria, Pyrenees, North Apennine, Central Apennine) the field with the wind directions nearest to those of the flight (about 4-6 Mb per JPG map). Then either

  • double click on the corresponding field to open, analyse and, if desired, save the corresponding map locally, or
  • right click on the same field and request the target to be saved directly in a directory of your PC.













Northern Apennine,
Central Apennine, Italy

View in Google Earth

A 3D view may facilitate the perception of a given wind situation, as illustrated by this example. Users having installed Google Earth© on their computer can generate such perspectives themselves.

WindMap is based on the same topographic data (SRTM) as Google Earth. A simple click links all WindMap files with Google Earth. In order to avoid a significant loss in image resolution, the original charts have been cut into tiles of 2 square degrees which are referred to at the lowest level of the Google selection tree. Therefore the selection hierarchy looks as follows

WindMap-3D > Region > Region+Wind direction> Tile (coordinates of lower left corner)

It is crucial to avoid maing selections above "Region+Wind Direction", to prevent Google to superimpose pictures with different wind direction.

The selctions appear as overlays on the Google screen. Picture transparency is set at 35 percent, but may be adjusted manually (right click on selection tile field > click on "Properties" > use transparency slider on top).

For Google Earth or software for flight simulations in Google Earth using IGC flight recordings please consult references 8 and 9.

Order CD

Accessing the internet through a high speed line is not always possible. It may then be simpler to access the maps directly on a CD. In Switzerland and the EU the CD is delivered against pre-payment. For this purpose you can send TherMap an order by E-mail with the following indications:
      • name, surname, address and phone number of client,
      • precise mailing address if different from client address
      • and indication WindMap

    and as a cost contribution for the delivery

      • within Switzerland CHF 40.- per map set on postal account CCP 18-16534-8 (Beda Sigrist, ch. de la Mulla 42, 1616 Attalens) , respectively
      • within the EU EUR 30.- per map set at the intention of account

        IBAN CH15 0900 0000 1801 6534 8 for payments in Swiss Francs
        IBAN CH82 0900 0000 9126 4004 8 for payments in Euros

        Receiver: Sigrist Beda, CH 1616 Attalens)
        BIC (Swift Code): POFICHBEXXX
        Name of bank: Swiss Post, PostFinance, CH-3000 Bern

    Deliveries are maid by ordinary mail as soon as your order and the pre-payment have been received.

  • Who is behind WindMap? Like TherMap, WindMap is a private initiative of Beda Sigrist, a Swiss glider pilot. Following the success of TherMap, Dr. Hermann Trimmel and Olivier Liechti encouraged him during the meteorological OSTIV conference 2007 at St-Auban/FR, to find out whether it was not possible to also generate sensible ridge wind maps. Several models were tried together with experienced competition pilots until the present map collection was established. On this occasion their invaluable contributions are acknowledged, particularly those of Stefan Leutenegger. Further thanks go to Aéro-Gruyère for continueing to host this website.

  • Can the application behind TherMap be purchased? It would of course be interesting to have available directly the source code needed to generate the maps. If the application itself was distributed, the product would have to be wrapped up as a professional package and update management procedures introduced to ensure that the users would always have available the latest version. The resulting costs would require a commercial approach. Apart from the much bigger effort, this would be in conflict with the conditions set by SRTM, the distributor of the satellite data, which is basically only made available for non-commercial use.

  • What possibilities exist to generate WindMap images reflecting the actual local wind conditions at a given time?
    This question can probably only be answered in the longer term. Today it is already possible to obtain wind forecasts with a resolution of just a few kilometers, and their precision is expected to further improve with time. Preliminary tests with data from Meteoblue as local input to WindMap already showed promising results in 2008. For digital data files it is however unavoidable to pay a certain price. But even with this data there would be the additional costs of permanently recalculating and publishing the latest wind map forecasts. Finally we must be aware that there are not so many days with good wind conditions and that the number of pilots interested is small.

  • Can WindMap be extended to other regions, e.g. outside Europe?
  • The development of WindMap, like TherMap, has also been the result of intensive information exchange with experts and experienced pilots, because the models represent only partly physical processes, the other part being rather models of the perception of experienced pilots. For any new region to be addressed it would therefore be crucial to have such competent and experienced counterparts to properly adjust and validate the models, if necessary. With such help from colleages of new territories it would however be a pleasure to extend the scope of WindMap beyond the present regions.


If you have any comments, suggestions, or questions,
you are welcome to write to TherMap/WindMap by e-mail.

Société d'aviation de la Gruyère S.A. CH-1663 Epagny Tél:++41.(0)26.921.00.40 / Fax:++41.(0)26.921.00.44