The GeoCaching Page of Prof. Y. Lupardi

made by Piet Vogelaar

I use my GPS12 on a motorized bicycle.

photograph of GPS on bicycle

More pictures and an explanation.

My maps

All shown topographic maps date from 1996 to 1999 and are digitized with marked RD-coordinates.
For the legenda (what are those symbols on the map?) see here for 1:25.000 (706 kb) and here for 1:50.000 (635 kb).
You can find the map-numbers (for 1:25.000) and the time of their last update in a picture here (33 kb).
The map-numbers for the 1:50.000 maps are here (29 kb). The dating of the maps (1984 etc..) is not right: it is a very old picture.
For use of these Dutch maps see the explanation GPS en plaatsbepaling voor biologen by Laurens Sparrius.

I have gathered information on how to set your GPS for use of the Dutch Grid. You can find it all on this separate page

My maps and Ozi Explorer

A lot of people have difficulties when using digital scanned and calibrated maps with RD-grid. For those I made a special RD&Ozi-help page.
A Dutch version of this story is here.
If you want to use the WGS84 system then there is here a story.

Aireal images (black and white)

All aireal images were taken in the spring of 1989 and that is a long time ago. Spot the differences with the situation of today by visiting the caches!

Satellite images (black and white)

All satellite images were taken between 1992 and 1994 by the SPOT satellite. These fotographs are ortho-rectified so it looks like you see everything from straight above. One pixel in the picture is 10 m in the real world. The numbers on the rim give positions in decimal degrees. A small green cross shows the position of the cache within a few hundred meter.

Aireal images in colour

In these pictures you look straight down from a hight of about 300 meters to the cacheplace. As you can see on the copyright notice in these pictures, they are made with Terra Explorer software.
When want to make your own pictures you first have to download a copy from the software here so you can use the pictures from this Dutch site. Read the manual and help-file first. Then try to go to a position by use of the navigation window. Point the camera straight down. The coordinates are in the Dutch RD grid notation.

Caches Hidden

The links named 'description' will give you not only an English text describing the cache but also more environmental information.

Creation date Geocaching page (Dutch) topo map 1:50.000 topo map 1:25.000English cache descriptionaireal b/w picture Satellite b/w pictureAireal colour pictureDutch RD-map coordinates
7/25/2001 'Leiden Urban 1' 131 kb 121 kbdescription 189 kb 215 kb 90 kb 093397/463364
7/25/2001 'Tuf-tuf' 198 kb 219 kbdescription174 kb 190 kb 58 kb 104754/457078
7/25/2001 'Biertje?' 183 kb 119 kb description 143 kb 193 kb 57 kb 096533/460744
7/28/2001 'Eindpunt' 228 kb 169 kb description 177 kb 191 kb 53 kb 102260/459056
7/29/2001 'Platland' 199 kb 285 kb description 198 kb 190 kb 53 kb 092204/458007
7/31/2001 'Waterval' 258 kb 155 kb description 130 kb 183 kb 58 kb 095493/457184
8/11/2001 'Leiden Urban 2' 135 kb 136 kb description 187 kb 215 kb 74 kb 094528/464184
8/14/2001 'Boompjes' 213 kb 244 kb description 186 kb 184 kb 57 kb 103625/455642
8/23/2001 'Uitzicht' 112 kb 265 kb description 103 kb 181 kb 59 kb 091105/474974
8/29/2001 'Drassig' 278 kb 179 kb description 99 kb 168 kb 54 kb 117440/462333
5/29/2003 'Brandnetel Eiland' n.a. 258 kb description n.a. n.a. 39 kb 088614/458970
6/20/2003 'Hold your Horses' n.a. 56 kb description n.a. n.a. 39 kb 085170/465775
11/22/2001 'Moeras' n.a. 205 kb description n.a. n.a. 39 kb 094414/456092

Special guest:

Mr. Bannerjee from Benares is a travelling guest. I have given him his own guestpage

My GPS12 accuracy

A lot is said about the HDOP (Horizontal Dilution Of Precision) and EPE (Estimated Position Error) but the proof is in the pudding. What have I observed in reality?
If you care to know click here.

The benchmark hunt

In the Netherlands there are many markers, some are 'zichtpunten' and others are part of the national RD-Kernnet. If there are no caches in your neigbourhood then there are for sure some markers for you to find and photograph. More details about the Dutch situation I have put on his page. You can read on a special page about my adventures in benchmarkhunting (In Dutch!). But beware: many photograph make downloading a long task.

Searching for the old railways

As in every European country we had many more railways in the old days. On topographic maps you can see traces of old railways. Sometimes they are converted to normal roads, somewhere else they simply disappeared beneath new buildings but many times they are converted to bicyclepaths. And in some cases only the rails and the bridges are removed and things are left to nature. A report of an expedition searching for remnants in and between Aalsmeer and Uithoorn, illustrated with many photographs (it takes its time to download!) is written by me.

Publications about me

Sometimes I am asked for an interview on the radio or asked by a newspaper about geocaching. When possible I will place a soundfile here of a 5 minute interview at Radio West at some later date. At the moment there is a scan of an article about geocaching in the local newspaper Leidsch Dagblad of aug 19, 2002.


Caches Found

Not much but the number is rising.

Benchmark hunting

For this variation on the geocaching game I have made a separate page here.

In short: find, describe and photograph markers that are on the official Dutch list and every other kind of positionmarker you find.


After the disasters of XI-IX new laws are made in Europe limiting civil rights. We now have Euro-Cybercrime laws extending national law across the borders. Some things are lawfull in my own country but not in another and there is no way to resist extradition. So regretfully I am obliged to add the following text to this website:
"Mit Urteil vom 12. Mai 1998 - 312 O 85/98 - 'Haftung für Links' hat das Landgericht Hamburg entschieden, daß man durch die Anbringung eines Links, die Inhalte der gelinkten Seite ggf. mit zu verantworten hat. Dies kann, so das Landgericht, nur dadurch verhindert werden, daß man sich ausdrücklich von diesen Inhalten distanziert.
Hiermit distanzieren wir uns ausdrücklich von allen Inhalten aller gelinkten Seiten. Diese Erklärung gilt für alle auf unserer Homepage angebrachten Links.
Alle auf der Homepage genannten Markenzeichen sind Eigentum der jeweiligen Inhaber."

Because of recent developments in the USA and the extradition treaty between USA en Dutch gouvernment I feel also obliged to add the next texts for legal reasons:
"Certain statements made on these webpages are forward-looking statements within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934, and are made pursuant to the safe harbor provisions of the Securities Litigation Reform Act of 1995. Actual results may differ from those set forth in this publication due to certain risks and uncertainties."


These pages are only intended for viewers within the jurisdiction of the Kingdom of The Netherlands. Others viewing these pages have to keep in mind that viewing my pages may violate their local laws or annoy their leaders. I do not take any responsibility for this on me. But please viewers, keep also in mind that I may be held liable by your local laws for making your (criminal?) behaviour possible. It would be very sad when I am put in prison when I visit your country on a holidaytrip. And maybe your country has an extradition treaty with mine so I can even be legally exported to your country.


Nothing on these pages falls under the international provisions of the U.S. Digital Millennium Copyright Act (DMCA)

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