WindMap© version 1.06- released
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.
A complement to TherMap
Français - Deutsch
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
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.
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.
||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
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
Depending on the extent of your flight you may have to select
the maps of more than one country or region
|| 48° 00'’ N / 05°
|| 45° 30'’ N / 11°
|| 48° 00'’ N / 09°
|| 46° 00'’ N / 16°
| French Alps
|| 47° 30'’ N / 05°
|| 43° 00'’ N / 07°
|| 43° 20'’ N / 03°
|| 42° 00'’ N / 02°
| North Apennine
|| 45° 00'’ N / 07°
|| 43° 30'’ N / 12°
| Central Apennine
|| 43° 30'’ N / 11°
|| 41° 00'’ N / 15°
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
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..
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.
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
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
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).
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.
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.
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
precise mailing address if different from client
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
CH15 0900 0000 1801 6534 8 for payments
in Swiss Francs
CH82 0900 0000 9126 4004 8 for payments in Euros
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
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
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.
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.
A website offering also forecasted wind maps:
Meteorological panel of OSTIV
If you have any comments, suggestions, or questions,
you are welcome to write to TherMap/WindMap by e-mail