Portuguese 888 series. Grid Help

I have purchased some of the Portuguese 1/25000 Military topographical
maps,from which I wanted to take waypoints to load into a Garmin GPS
Map60csx. I am having difficulty understanding on what grid system the
maps work.

The main grid ,I thought was UTM, but if I test a few waypoints using
this grid against the same points refernced in Google Earth ,I find
significant errors that lead me to believe that is not correct.

Equally if I use the secondary long/lat grids used on the map borders
,I do not get a correlation there,either.

I expect there is something in the legend that would help me,but I dont
read Portuguese!!

You might say-why not just use GE, but in many of the areas I'm
interested in the resolution is just too poor.

I'm a bit stumped ,can anyone help?

Patrick

UTM is correct - but the older maps do not use WGS84 - the map datum is
ED1950 or Lisboa.

see: http://snig.igeo.pt/inspire/DOCUMENTOS/rcrPTv4.pdf
http://www.asprs.org/resources/grids/04-2002-portugal.pdf

hth
Anton

Anton Betzler wrote:


Thanks Anton,I will give that a go when I get home tonight. The first
link would not open, but I see the conversion factors towards the end
of the second article,I presume I try each and see which gives me the
correct answer against a known point in GE or Mapsource.
Once I have established that ,will it hold for all of that series of
mapping?
Patrick

Patrick wrote:

You are correct, the M888 series has a superimposed UTM grid. In the
older maps the datum is ED50, in the the newer ones (from May 2000
onwards) it is WGS84. You can easily tell them apart because the ED50
grid was printed in blue and the WGS84 grid is now printed in black.

There were some really old M888 maps, from the early 60's, that had a
Gauss grid, printed in brown. I think these old maps were all replaced
and are no longer sold.

HTH

Carlos

Thanks,Carlos and Anton,for your help. Got it all sorted now.
Patrick