Note from Waldy on the map data and coordinate system for the GIS files.

to calibrate the Garmin GPS unit using user define coordinates and datum NAD 27 for Central America. If you enter these data you are able to get lambert coordinates for Costa Rica in your unit.

Lambert NW Costa Rica:
longitude origin 84 deg 20.000'
scale 0.9999600
False East 499800.00 m
False North -885250.0 m
Units = m

I am using Arc View 3.2 and we use an opcional extension call CR PROJECTION DATUM to work with lambert coordinates and you can change it to another coordinate system. Probably it works similar with ARC GIS 9.

You have to charge this extension in Arc View. In adition you have to create a folder called temp in the root of your C C:\temp and save in this folder the file called DATUM.PAR

When you open Arc View activate the extension CR PROJECTION DATUM and you will see three new icons in your monitor

You can use this extension to convert data from Lambert CR Norte to gg.ddd.

Another way to work with Lambert data for Costa Rica is to configure the Arc View program.

Follow these steps

Open Arc View
Add a view
In the option Map units choose decimal degress and choose meters for Distance units.
Go to Projection Properties and click Custom
Find and choose projection Lambert Conformal Conic and Clarke 1866 for the Spheroid

LAMBERT NORTE
gg.m.s.dd gg.ddd
Central Meridian 84° 20' 00" W -84.3333
Reference Latitude 10° 28' 00" N 10.4667
Standart Parallel 1 09° 56' 00 9.9333
Standart Parallel 2 11° 00' 00" 11.0000
False Easting 500 000.000 500 000.000
False Northing 271 820.522 271 820.522

Once you open a file with this changes if you want to keep the change you have to convert to shape file in order to be able to work with other coverages using Lambert CR Norte.