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Everything posted by brad.32

  1. Yeah, a walking stick is too big to leave, even if it did fold. As a pole, it would definitely be a "look here" sign. You could carve a mini-walking stick or something like that (other carved item) and leave them as your signature item. Signature item are nice finds in caches. ... or the coupon idea of Mopar's.
  2. Longitude and latitude coordinates are used for a geographic coordinate system, which are locations on a 3D spherical surface, not a projection. The spheroid is based on a datum. The spheroid defines the shape and size of the surface and the datum defines the position of the spheroid relative to the center of the earth. The datum is a frame of reference (the origin and orientation). Early datums were local and not based on the center of the earth, but a particular area on the earth. NAD27 is/was designed to fit North America, particularly Kansas. NAD27 is based on the Clarke 1866 spheroid, which was based on the best surveying measurements and calculations of the day. NAD83 is based on the GRS1980 spheroid, which is an earth-centered spheroid derived from ground and satellite data. The GRS1980 and WGS1984 spheroids are almost identical, so the WGS1984 and NAD1983 datums (both earth-centered) are very similar. A projection uses coordinates on a flat, 2D surface. These projected coordinates are calculated from a transformation of the 3D surface into the flat surface. The spheroid and datum define the shape if the 3D surface. The projection defines the transformation. The flat surface is usually a cylinder (Mercator and UTM) or a cone (Albers Equal Area), but sometimes a plane. [This message was edited by brad.32 on March 17, 2003 at 02:37 PM.]
  3. I had an email from him too, and replied, BEFORE seeing this thread. Why would he contact so many people to ask a simple question like that? Sniff sniff. Smells like ... sniff ... email address harvesting. SPAM SPAM SPAM.
  4. I sometimes train people to use ArcPad to collect geocoded attribute data and digital images. (People who don't use ArcView or ArcGIS face a learning curve.) They don't really need to know how to navigate to a waypoint, because they will be recording points and acquiring data there, and not (usually) making repeat visits. When my family goes geocaching, I use a point shapefile to record the cache find, including the date and exchange information. These data are not "useful", but the activity seems like it would be an interesting exercise for someone learning the software and collection ... procedures. Is geocaching too much like fun to include in PocketPC and GPS field data collection training?
  5. You could do searches on the cache search page for "hotel", "TB hotel", "bug hotel", etc. The results will show the location state. Have you tried that?
  6. Letterboxing is similar to geocaching without a GPS and you may find it interesting. http://www.letterboxing.org
  7. ummm, why not just use a CF GPS when you're interested in using the software and display on the PocketPC anyway? Those cables are annoying. ouch.
  8. "The Monte Carlo method, as it is understood today, encompasses any technique of statistical sampling employed to approximate solutions to quantitative problems." http://www.riskglossary.com/articles/monte_carlo_method.htm It's the use of a large number of randomly generated trials to come up with estimated results. You let the computer do the work, so you don't have to do the math.
  9. Yes, what I did is a Monte Carlo simulation, I just didn't call it that because I figured geocachers wouldn't be familiar with the term. ... so, Moe, what do you calculate for the combined error?
  10. This is off-topic, but I was curious about this one... The maximum error for two different GPS units is the sum of the maximum errors like Brainsnat wrote, but what is the typical error? If the cache placer and the finder go to the same place on different days, they are using a different configuration of satellites with a different PDOP, etc. I would think that makes them independent measurements with a different amount of error. Assuming a point (p) with a random error of up to e in x and y (the placer's coordinates of the cache), around the origin (the TRUE location of the cache), and a second point (f) with a random error from p (the finder's coordinates for the cache), what is the typical distance between the second point (f) and the origin (the finder's error from the cache)? For 10000, 100000, 1 million, and 10 million trials, it's about e. This shows that the random error does not compound, but only forms a relative error the same as the error of each measurement.
  11. ... and include extended TB instructions with it. People don't seem to get log them without more instruction on the bugs. (When is Groundspeak going to improve the tags?)
  12. quote:Originally posted by BrianSnat:You have to remember that your GPS has a margin of error and so did the cache placers unit when he hid the cache. If yours was accurate to within 25 feet and the placers was accurate to within 25 feet whe he placed it, you could be as much as 50 feet off. Exactly, but your GPS unit, and everyone else's, DOES have an accuracy of 5-10 m. There is no "if". The original question was whether there was something wrong with his GPS. No, 5-10-m error is normal.
  13. quote:Originally posted by logscaler:Not sure about the 310 but the 315 and the 330 will allow the display of both wgs84 and utm on the screen at the same time. If that is what you want to use, use it. The datum is the spheroid, not the projection. UTM is a projection. WGS84 is a datum. The 310 and higher can all display UTM and lon/lat coordinates. I don't know about "at the same time" though.
  14. Accuracy refers to correctness. Precision is repeatability and uniformity. A measurement can be precise, but still be wrong over and over again.
  15. Jammed GPS signals would mean missing the targets and hitting civilians and civilian targets. Hmmm. There are pros and cons to that in Iraq.
  16. It's all about clocks. John Harrison is our hero. When Captain Cook took Harrison's extremely accurate clocks (for the time) on his voyages, that greatly improved his ability to navigate and map the globe. GPS technology works because of accurate clocks. Light travels about 1 ft / nanosecond. Spatial accuracy depends on the ability to measure time accurately.
  17. brad.32

    Older GPS

    I don't know if the 2000 is limited in its ACTUAL accuracy, but if you switched to UTM it will DISPLAY to the nearest meter. Best case the error will be 5-10 m, like all standard GPS units.
  18. The Canadian Center for Remote Sensing has a bit under their imagery and sensors pages, http://www.ccrs.nrcan.gc.ca, but they also have a link to GeoGratis, http://geogratis.cgdi.gc.ca. They have vector and raster data, though they don't seem to have any satellite imagery that is high spatial resolution.
  19. You should able to set your GPS unit to display/use UTM coordinates through the setup, then use the coordinates on the caches pages. GCM? "General circulation model" and "global climate model" are the only ones I know. GCP would be ground control point. What was the context for that one?
  20. quote:Originally posted by Renegade Knight:...I have to look at people funny when they say "so you take a gps and walk right up to the cache...that's easy how hard can it be?" They haven't geocached in a redwood forest. "Last time I had a position we were about 800m away." "What are we now?" "300, so we're on the right trail"
  21. Oops. I was looking at the 315. Yes, the 310 can only show lon/lat in DDD MM.MM or DDD MM SS, like canadazuuk wrote. You'll have to display in deg/min/sec and convert the decimal minutes used on geocaching.com to minutes and seconds. 60 is a nice round number. ... or get a better GPS unit.
  22. You should be able to change the format to DDD MM.MM, DDD MM.MMM, or DDD MM SS through the setup menu. You are apparently in DDD MM.MM mode now.
  23. I haven't seen mention of those, but there is "Skan's CacheCard project" http://cc.flame.org/, which sounds similar.
  24. For short distances, like walking, it doesn't matter what projection you use (UTM, Lambert Conformal Conic, or Integerized Sinusoidal [ugh]), you can calculate relative coordinates using bearing and distance. For longer distances, a projection that is azimuthal is better (represents angles better).
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