TherMap© version 2.0 - released Feb. 2011
On August 6, 2008, on the occasion of the Opening of the
Gliding World Championships at Lüsse/Berlin, Germany,
Dr. Beda Sigrist a diploma for this innovation, considered
the work to be " a quantum leap in analizing and
optimizing flight paths in known and unknown orographies".
The utilization of these maps for non-commercial purposes
remains free. For commercial uses, quotations, as well
for further publication written copyright permission must
be obtained via the mail address mentioned at the end
of this site, and this site quoted as the source.
For ridge wind maps see WindMap
Français - Deutsch
Position the cursor on the picture
below and you can see a map extract of TherMap, a tool for glider
pilots, to visualize the local potential of thermals on digital
maps on a given date and hour, assuming favorable meteorological
conditions. For any sensible time and date of interest, thermal
hotspot maps can be downloaded from this site free of charge.
A second possibility is to directly
overlay the maps on Google Earth
, which offers further viewing
facilities such as 3D perspectives or flight simulations visualizing
the thermal hotspots. Finally, a complet set of the country maps
can be ordered on a DVD
at a cost covering charge, covering
Switzerland, Austria, the French Alps, the Pyrenees, the Northern
and Central Apennine, Slovakia, as well as the American Sierra
Nevada between 35 and 43 degrees latitude.
Unlike other thermal maps, which are usually based on statistical
analyses of flight paths, thus essentially just showing "trodden
flight paths", the maps of TherMap have been derived solely
from the orography ( cf. model outline
The maps therefore also show the potential of thermals in less
Before the flights TherMap maps permits to study the best itineraries,
or to explain them to less experienced pilots, particularly across
less known regions. After the flight, flight logs (typically IGC-files
converted to KML for use with Google Earth) may be superimposed
to these maps, to find out where more promising paths might have
What is new in TherMap 2.0
To make the maps easier to read and to facilitate the orientation,
TherMap 2.0 shows areas with lower thermal potential only as topographic
backdrop surfaces. In relatively flat areas, where the TherMap
model can provide little guidance, significant elevations within
a radius of about 1 mile are now highlighted by an "x"
mark, as those could be an additional hotspot locations. Following
a request of Sergio Colacevich, a well-known American glider pilot,
the 420'000km2 region of the US Sierra Nevada has been added to
the menu. For the time being, the previous maps of TherMap 1.06
can however still be accessed via a crosslink in the download
In January 2012 the surface of
the US Sierra Nevada region was extended to the Pacific coast.
To access the extended region on Google Earth you must ractivate
the corresponding kmz-links by pressing here.
Following requests, special guidelines have further been added
- How to open OLC flight tracks
in SeeYou and view them on a raster map of TherMap
- How to open OLC flight tracks
in Google Earth and view them on a overlay map of TherMap
a. How to read the maps
b. Flight preparation
c. Reviewing flights
d. Limitations of TherMap approach
Zooming: The maps should
be zoomed at least to 100 percent. Original maps may contain
about 10 Mb in JPG format, which corresponds to about 30 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 downloaded images.
of the temperature and the irradiance maps vary from green
to yellow and finally red. Assuming a glider with a minimum
sinking rate of 0.5 m/sec the colours represent approximately
the expected climbing rates shown on the following graph:
Green areas, e.g. in relatively flat regions or at the end
of the day, can still indicate how to best stretch a flight
path, whereas during peak hours in mountain areas une can
basically focus on the red colours only.
3D visualisation: Using the Google
link below, linking TherMap with Google Earth® takes only
seconds, whereas importing them for instance in SeeYou®
(as raster maps) is more complicated and takes several minutes.
A further advantage of Google is that "flight" routes
can be simulated, which is useful for flight preparations.
For flight reviews, which can be useful to study alternative
flight paths, several free conversion programs can be found
on the Internet to convert IGC flight record files into KML
files. Upon clicking on these files they open with Google
a calculated solar irradiance and a non-stable atmosphere
responding to temperature increases. It is therefore only
usable on sunny days with good meteorological conditions,
i.e. en unstable temperature gradient and sufficiently high
condensation base. In other words, TherMap is a complementary
tool to meteorological forecasts
, but can in no way replace
these. It is up to each pilot to learn and determine, when
the conditions are suitable to make use of TherMap. In case
of predominant winds it may further be worthwhile to consult
Checking planned flight paths:
TherMap is best used before the flight to check the local
conditions at the expected time of overflight (e.g. when to
change to the other side of a valley) and to note possible
alternatives in case of unexpected changes.
In-flight use of TherMap: Consulting
a map during the flight must not interfere with the necessary
observation of the flight space. Tests with mobile navigation
devices, into which TherMap hotspots had been imported,
have shown that this represents a risky distraction from
flight observation, further aggravated by the poor readability
of present displays. However even with better displays,
the mobile tools should be designed to automatically show
the hotspots valid at the actual time, to avoid manual file
manipulations distracting the pilot.
This requires the flight tracks to be
traced on the maps closest to the date and time of the flight.
Besides identifying possible alternative flight paths, such
analyses also help to better interpret TherMap. Due to the
ease of activating the maps on Google Earth, the latter tool
is preferrable for such analyses, because it does not require
importing (raster) maps into flight planning aplications.
On the other hand, the latter tools offer the known additional
features of these specialised tools.
If needed, the following links open guidelines for making
such analyses either with SeeYou
or Google Earth
Colour coded thermal pressure
map in 3D-view with vario-flighttrack
(reproduced using SeeYou© on the basis of an imported thermal
d. Limitations of TherMap approach
Limitations of radar maps:
Radar reflection signals are not perfectly precise when
scanning altitudes (precision about 5m). They are particularly
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 TherMap 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. Some ice covered surfaces appear blurred.
Fortunately neither of these limitations seems to limit
the use of the maps.
Wind drift: The further
away the glider is from the ground , the more its flight
path may be shifted in the direction of the wind drift.
Such shifts can be visible on TherMap flight tracks on a
Borders of plains: Air heated
over plains can be shifted by slight wind until hitting
a small edge or elevation, thereby triggering a thermal.
At present TherMap does not map such locations.
Other effects: TherMap
only shows the solar heating effect causing thermals on
slopes. At certain locations other effects can however be
stronger than the thermals, e.g. due to cloud covers, or
wind, particularly at narrow valley entrances, but also
where the air is cooled by lakes or ice covered surfaces.
N / 05° 30’ E
N / 11° 00’ E
N / 09° 30’ E
N / 16° 20’ E
N / 05° 00’ E
N / 07° 30’ E
N / 03° 00’ W
N / 02° 30’ E
N / 07° 30’ E
N / 12° 30’ E
N / 11° 30’ E
N / 15° 00’ E
N / 18° 00’ E
N / 24° 00’ E
US Sierra Nevada Very
N / 125° 00’ W
N / 115° 00'’ W
US Sierra Nevada North
N / 125° 00’ W
N / 115° 00'’ W
US Sierra Nevada Center
N / 123°30’ W
N / 113°30'’ W
US Sierra Nevada South
N / 122° 00’ W
N / 112° 00'’ W
Depending on the flight you may have to select one
or more of the countries or regions
provides maps of selected dates from the beginning of
April to the middle of September (Months 4 to 9). Select
the maps showing the date closest to the flight date.
The map date/time is included in its file name (month-day-hrZ)
UTC is now generally used, whereby
3 map times per day have been included in the map collection,
namely one for the latest full hour before the highest
elevation of the sun, and two others 3 and 6 hours later,
respectively. If we tolerate that the map-time may differ
up to 90 minutes from the flight, these three maps basically
cover a total time interval of up to 9 hours.
UTC is normally also used in the flight records.
Select the map closest to the time of overflight.
A longer flight will therefore require several maps.
This also applies to flight analyses, for which we
recommend however to make use of the Google Earth
overlays of TherMap.
The following table contains maps generated by TherMap2.
The TherMap1 menu with the entirely
colour coded maps is however still available.
Each of the OK fields of the following table represents
a map of a region at a given date and time. Select the one
closest to your flight path. (about 6-10 Mb per JPG map).
Then either double click on the field of the map to be viewed,
or right click on the target field and request the map to
be saved directly on your PC.
The complementary maps either show the basic topography
or the slope determined view of the region.
All maps of this
collection are provided by the copyright holder solely
as an informational tool for the planning of the best
course of soaring flights. In particular, airports and
landing places are indicated mainly for geographical
reference without guarantees about their exact location
and/or their operational conditions. These maps are
not intended to be used for navigation. Pilots should
independently confirm all information regarding airports
and landing places and other information required for
navigation, and obtain an official briefing before flight.
In no event shall the copyright holder or the contributors
be liable for any direct or consequential damages caused
by incorrect, obsolete or missing graphical or written
The copyright holder:
Beda Sigrist, Switzerland
with Google Earth
A 3D view may facilitate the perception
of a thermal landscape, as illustrated by this example.
Users having installed Google Earth©
on their computer can generate such perspectives themselves
and/or simulate flights in a "landscape with visible
thermals". In addition actual flight records (converted
to KML file format) can be superimposed to review a
TherMap is based on the same topographic data (SRTM)
as Google Earth. It is possible to link TherMap files
with Google Earth within seconds. Before doing this
you should be aware of the following:
In order to avoid a significant loss in image resolution
(due to a constraint of Google Earth), the original
charts had to be cut into tiles of two square degrees
which are therefore referred to at the lowest level
of the Google selection tree. TherMap actuall had to
generate almost 3000 tile files for this purpose. The
resulting Google selection hierarchy looks as
(1) TherMap2-3D> (2) Region >
(3) Region+date+daytime> (4) Tile (coordinates
of left lower corner)
It is crucial to never select the
maps above the level of the "Region + Date + Daytime"i.e.
level 3. Above this level Google overlays all maps
below the level selected, e.g. all dates and
daytimes of a selected region, which would be meaningless.
It is however also possible to activate several adjacent
regions for a specific date and daytime. Note that loading
the tiles still takes a few seconds with Google Earth.
of how to use Google Earth:
Suppose you want to see the area around
Lake Mono (US) on June 1 at 19hUTC,
click on the link below: "US Maps
(Sierra Nevada)" and confirm that
you want to open this link with Google
Earth, upon which the Google screen
at left first click the "+"
box to expand the map selection e.g. "TherMap2_USA-3D".
You will see the regions available.
the "+" box of "SraNevd_C"
(i.e. the Sierra Nevada beween 37 and 39 deg
Google then shows the dates and daytimes available
for this region.
empty square on the left of "SraNevd_CJun1_19hZ"
to select all maps for this region ,date and
time. Google then switches on the map tiles
of this region and adds the list of these
the tiles you do not need. In our case these
are the ones ending with 37N117W, 38N117W,
37N115W, and 38N115W, leaving
the four map tiles around Mono Lake. Then
zoom into them...
Google overlay picture transparency
is set at 20-35 percent, in order to still perceive
the underlying Google landscape. The transparency can
be changed manually at tile (= lowest) level by right-clicking
on the selected flield, then clicking on "Properties"
and finally adjusting the transparency slider
on top of the property window.
a DVD of the Maps
Accessing the internet through high speed lines
is not always possible. It may therefore sometimes be simpler
to retrieve the maps directly from a DVD. The maps of TherMap2
can be delivered against pre-payment in Switzerland and the
EU . For this purpose pls 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
- the desired DVD: TherMap2
and make a pre-payment for the delivery
Deliveries are made by ordinary mail as soon
as the order and the pre-payment have arrived.
Some links to Topterm users:
Meteorological panel of OSTIV
Sergio Colacevich: Sierra Nevada Great
Basin TherMaps, Soaring
If you have any comments, suggestions, or questions,
you can directly contact the author Beda Sigrist by e-mail