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Entropy512

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Everything posted by Entropy512

  1. Hi I presume you are in america or canada? The Iphone app is great but it would be nice if tied it in to the sat nav for driving directions. The big problem with the Iphone is the gps is not very accurate in England, I dont know why because the Ipad is good to 2m and the ip4 is surposed to use the same electrinics? so Iphone 4 in england no! The iPhone 4's antenna design (for all antennas, as far as I can tell) is best described as "epic fail". I'm an RF engineer and so are a number of my coworkers - the moment we read about the issue and then saw the actual design we started laughing out loud. Any device where the antenna is in a position that a person's hand will normally contact the antenna element is STUPID. It's understandable that on a phone-sized device you'll deal with some nasty blockage issues, but designing a device with bare antenna elements that are part of the casing if the device is 100% idiotic. So yeah, I'm not surprised the iPhone 4 has poor GPS reception.
  2. Have and Use Often: Oregon 300 AT&T Tilt 2 i-Blue 747A+ logger/Bluetooth/USB puck (MTK2 chipset) Generic Chinese 5" Windows CE PNA device from DealExtreme Still own but shelved: AT&T Tilt AMOD AGL3080 logger (no Bluetooth) (SiRF III) Holux GPSlim236 Bluetooth puck (no logging) (SiRF III) Used to own: DeLorme PN-40 - returned when it died after 2 days Garmin eMap - Parents have this now, my first geocaching GPS Garmin GPS 45 - Technically I didn't own this, but parents did when I was in high school and I was the operator most of the time
  3. Another possibility not covered here is that the cache was in sight, but you didn't see it. This is especially likely for micros. Some of them are EVIL - you can be looking straight at them from 4-5 feet away and not realize it. As an example, I remember one cache that was hidden near a bathroom. There were a few plastic sewage ventilation pipes sticking from the ground near the bathroom, however one was slightly oddly placed. It turned out to be the cache. I would have stood right next to it and not realized it if I hadn't decided to read the hint.
  4. Which eTrex? There are quite a few. Some have a built in electronic compass that can determine which way the unit is heading even when at very low speeds. (In my opinion, an EXTREMELY useful feature for geocaching.) Others do not, and can only give you heading information when moving. Note that these will only tell you the direction you're moving, not facing - so if you walk fast backwards everything (waypoints, maps if applicable) on the screen will be upside down.
  5. Garmin is the way to go for non-Windows users. Garmin has a Mac application for map management, everything beyond maps can be done with basically any operating system. I do nearly all of the management of my Oregon 300 within Linux, no special software needed. Everything but Garmin's IMG map format is based on open standards (GPX, KML, etc) now.
  6. With the exception of the high grade precision antennas (like that Trimble with the choke ring collar to reduce multipath), there's not much you can do to improve GPS reception. The key here is: If you have LOS, you'll have good signal. If you don't have LOS, the satellite signal will contribute to errors if you receive it. Also, you can't use a "high gain" antenna, since high gain antennas are fundamentally directional - a GPS antenna needs to cover the whole sky evenly.
  7. It seems to me like over the past month or two Garmin has popped out some pretty significant upgrades, if anything their update rate for Oregons is higher than average now: BirdsEye WAAS fix Cache filtering They may be in a final "test and cleanup" phase before their next non-beta release and don't want to pop that out too early.
  8. Another possibile contributor to reduced usage of GPSBabel these days may be the fact that many new GPS units support the GPX format natively. As a result, I haven't needed a format conversion or loading utility for quite a while. I used to use GPSBabel for converting NMEA logs from an Amod AGL3080 tracker to GPX, but since switching to an i-Blue 747A+, BT747 has built in GPX and KML export. My Oregon 450 accepts GPX natively, so I haven't converted a PQ in ages.
  9. Anything cellphone based is NOT legal for a weather balloon. Most of the weather balloon groups look at FAA regs and say "we're legal!", without looking at FCC regs regarding airborne cell phones. If you obtain an amateur (ham) radio license, APRS will do the trick for you. APRS on VHF (144.39) was one of the two primary tracking methods used by Project Blue Horizon this year - http://www.projectbluehorizon.com/ - the secondary method was (if I recall correctly) slowly tapping out position reports in Morse code from a small HF radio. The PBH project is one of the few recent HAB projects I've seen that was fully legal including their comms/tracking system. (Half of the team members held ham licenses.)
  10. The 450 has basically superseded the 300 - most vendors sell the 450 for LESS than the 300 despite the 450 having more capabilities. I'd expect the 300 to disappear soon. The 400 series were just 300s with extra memory and preloaded maps. The 550 adds a camera and that's it I think.
  11. The problem is that, except for maybe as an overlay on the image data itself, it is not possible in most video formats recorded by camcorders to store metadata about video clips. (AVCHD does have some limited metadata support in the file structure, but probably has no provisions for geolocation metadata.) If you're doing timelapse, then you just need to geotag the stills. Actually you only need to geotag one still. For that purpose, any camera that saves the "Date Taken" EXIF field (basically any digital camera...) is all you need. Take your pictures, save a GPS log at the same time, then correlate the images to the GPS tracklog in post. If you're doing timelapse photography, doing the postprocessing step of correlating images to a GPS track is going to be nothing compared to the rest of your workflow. (It takes me about 30 seconds to geotag an entire directory of images in digiKam, gpicsync and GeoSetter should be similarly efficient.)
  12. For creating Garmin Custom Maps compatible KMZ files, I've been very happy with a GDAL + MAPC2MAPC workflow. GDAL is a great library (with included utilities that expose most library functionality as a commandline app) for working with georeferenced raster data from various sources.
  13. Which GPS are you using? Newer Garmins support drag-and-drop of GPX files right to the unit.
  14. Trail data for some but not all trails is included. Do you have a unit capable of using the Garmin Custom Maps function? You can use that to load a trail map into the unit.
  15. Unfortunately there are still plenty of people in this world who think NiMH cells suffer from "memory" problems like the old NiCd cells did and they like to deep-discharge them to keep it from happening. The truth of the matter is NiMH cells don't tolerate deep discharges like NiCd cells do and modern NiCd cells don't suffer from voltage depression (the correct terminology) like the early cells did. And the deep-discharge misconception apparently isn't a consumer exclusive. There are commercially available battery charger/cyclers that discharge cells well below the acceptable threshold for NiMH chemistry and the people who are engineering them either don't have a clue or are deliberately trying to encourage new-battery sales. Pete I believe that there is indeed a "memory effect" in NiCd cells, but it's actually very small and nearly impossible to reproduce outside of a lab. 99% of the situations that people think are "memory effect" are just overcharging damage due to dumb timed chargers.
  16. I went for a test walk with the new 3.82 beta firmware (one version after the big WAAS fix), with aerial imagery of my town park loaded. The GPS was actually accurately displaying which side of the road through the park I was walking on!
  17. I've always been under the impression that the of the two primary sources for error, the clock error was considerably more significant than the propagation error. It would be fascinating to see the actual data used across the entire service area. That would allow one to get the answer to the above very quickly since on a per-satellite basis, the total error for all geographic areas would be biased equally by the clock error in the total. I'll see if I can dig up my old notebooks from GPS theory class, but the main contributors to GPS error are multipath and ionospheric delay. Ionospheric delay is such a major contributor that the military designed the system specifically with ways to auto-correct it (but didn't give civilians that capability - autocorrecting for iono delay is what the military L2 signal is for. Once L2C goes live civilians will be able to autocorrect iono errors without external corrections.)
  18. I use the batteries in a number of devices, some of which will pretty much instakill alkalines in addition to providing deficient performance with them. (For example, any digital camera or camera flash that uses AAs.)
  19. It seems that in many locations, Garmin and DeLorme offer (at best) USGS DOQQ imagery. This is very low resolution compared to what many US states have. So far for many states, they have done their own aerial surveys with much higher resolution imagery than USGS DOQQs. Pennsylvania is 2-foot resolution in most of the state and 1-foot in some areas. New York is 1-foot for most of the state, 2-foot for some outlying areas, and 6-inch in some regions such as Ithaca, NY. New Jersey is 1-foot statewide. In general it seems that where available, Google Earth includes this imagery. Google Maps does not always include the state imagery. These datasets are available for free and small chunks of them can be loaded to Garmins using the Garmin Custom Maps function, but large regions require the DeLorme or Garmin subscription-based services which offer lower resolution.
  20. The correction data is not only about the wrong position of the satellite. It is about how the radio signal is distorted by the atmosphere, which varies depending on your location. OK - a bit of semantics there. There isn't technically a "wrong" position, it's an error in assumption about position by a ground receiver based upon environmental and clock factors. Point is that 48 and 51 aren't sending data with these errors incorporated and then sending correction data for themselves - none of which matters unless they're being used for a position solution anyway. Hence, a "D" has no real meaning for those two satellites. Some environmental factors (mainly ionospheric delay) are receiver location dependent, so you can't send a "precorrected" ranging signal that is common to all receiver locations. Plus this would break non-WAAS-capable units (which may be able to range off of the WAAS bird but not apply its corrections), so the ranging signal must be a normal one that has correction data broadcast for it. If it is true that these sats are sending ranging data, it makes sense to send location-dependent ionospheric correction data for that ranging data.
  21. I would set the lower limit for "cheap charger" to be one that still charges cells independently. This is a critical function to keeping multi-cell sets going. Otherwise one cell will progressively get weaker and weaker relative to the others. As far as which hybrids - Right now they seem to be all performing about the same. It's the non-hybrids where some manufacturers are sneaking "ultra low capacity" units that don't have a published capacity spec because they're in the 1500 mAh or lower range. I've had good results with Duracell Pre-Charged and Kodak Pre-Charged hybrids.
  22. Woohoo! Time to drop the filters out of my PQs (and drop my number of PQs too!)
  23. Any accuracy estimate other than DOP numbers are just that - a wild estimate that varies from manufacturer to manufacturer, and sometimes from receiver to receiver.
  24. Not sure. Many Verizon phones locked the GPS to specific applications, but I thought none of the Droids did.
  25. If you don't need the camera, you can purchase a Garmin Oregon 450, or Oregon 450t for less money. Plus, there is a $50 rebate from Garmin right now. Given that there are 24k topos available for free from gpsfiledepot.com, I would recommend the 450 over the 450t - the extra $100 or so for 100k topos just isn't worth it. The caveat to that is that the topo maps on gpsfiledepot suck... atleast the ones I found for California. Maybe the ones for the back east regions are better, but the one I installed was terrible. It doesn't have labels for anything, no city names, no feature names, just contour lines and points. Check gpsfiledepot first and make sure they have what you need. Their selections is very limited for certain areas... not every place is covered. If it were my decision, I would get the 450 and buy the Garmin topo maps. That way I would have a spare copy of them for if and when I decide to buy another GPS. I was very happy with the Northeast Topo map series.
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