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Posts posted by kerecsen

  1. That is one WEIRD approach to handling it, but it is what it is. Wonder why they just didn't put in a menu to manually delete what you didn't want on there - seems easy enough.


    Because the design of the whole map handling concept is based on the idea that Mapsource builds one big tree structure representing all the map segments available in the GPS, and transfers it to the GPS' memory. So when you load multiple maps, they end up as one big binary structure (one file), and deleting a part of it is somewhat like trying to stuff the toothpaste back into the tube. There also didn't use to be a file system on the storage cards, and the big-blob-file approach doesn't require one. (A file system in a simple device is a Bad Thing, because it introduces a lot of complexity such as fragmentation and possible inconsistencies/corruption.)


    Garmin handheld GPSes have very limited computing performance, to keep them cheap and to make them run days on two AAs, so every little bit of optimization counts.


    In addition, this overwrite-all solution can be explained to the average nontechnical user in two sentences, and doesn't require any sort of additional user interface.

  2. it could be... in which case it would be very good i was wearing a helmet and working (ski patrol) so no one could yell at me for doing 62 (or 70) by the slow sign.


    So you are the bastard that passes me in the slow zone when I'm trying to be considerate and slow down to the mid 40s :huh: Btw, how do you ski in Tucson?!

  3. I wonder whether the signal is directional, or could you get signal above the satallites too?


    I think all satallite signals are directional - why waste all that energy sending signals to Mars?


    They are most definitely directional. Look at these drawing and picture:




    The candy-canes are quad-helix antennae...


    Aside from the obvious waste of energy of putting out a signal in a direction where nobody is going to listen to it, the other advantage of the directional transmitter is that you avoid all chance that the signal gets reflected by another orbiting object and confuses the receivers on the ground. The disadvantage is that you can't use the GPS system to navigate a moon landing -- but then again, you may not need turn-by-turn voice guidance for that anyway...

  4. I am Sagi, a new member from India, Bangalore.


    Would like to buy a GPS and use it in India for caching purpose.


    For whatever it's worth, when I was in Bangalore I used my PDA phone + GPS for navigation, and it worked just fine.


    I used the Garmin world map (very limited, not particularly accurate, but useful for trips in the county side) and I also scanned in a Bangalore street map (from a foldable paper map) which I calibrated based on Google Earth. The scanned map turned out to be quite surprisingly accurate (especially after a bit of recalibration based on a couple of track logs). I could actually do street navigation with it. At least for those streets that were even marked on the map -- Bangalore isn't exactly famous for having street names or up-to-date maps.


    The image-based map is not nearly as convenient as an actual navigation-enabled digital vector map, but it is far better than being lost :)

  5. Thanks for the very good info. I view EMI suppression as an art not a science. I remember spending a very long night trying to get a computer FCC certified. The bead doesn't necessarily need a loop. It is the total current through the bead. A single loop simply doubles the current and doubles the effect. If I remember right we split the wires on a cable and put a bead on the shield only. Putting a bead on all of the wires had no effect. I'm guessing all of the current leaving came back on the return wires(twisted pair and not differential). Our problem on the shield was caused by a separate ground path(ground loop?) I was told by the EMI engineer.


    You are right, I didn't really think it through. The ferrite bead should work even without a loop. Now I googled the topic and it turns out that multiple turns will in fact increase the likelihood of amusing resonance effects that may end up increasing overall EMI. Which just reinforces my original conclusion: if you try to mess with the EMI, the EMI will mess with you right back :(

  6. The "can" is a ferro-magnetic bead or ferrite. It is a filter or "sponge" that absorbs EFI or RFI (electromagnetic/radio frequency interference) traveling along the cable that can get into your device or computer. They are good to have and you will see them on quality cables. You can add your own with clip on type. I add these to every cable entering or exiting my computer because I can hear the interference in my sensitive radios.


    Let me extend on what EScout wrote. There is a lot of mythology around this topic, and some of the answers on this forum highlight the most common misconceptions.


    What is the "can" for? In short, it is helping the cable behave less like a radio transmitter. It is trying to stop your computer and/or GPS from becoming a radio tower, and isn't doing anything to help your computer function, or to improve USB communication between the GPS and the computer (quite the opposite, in fact).


    Here is a bit of background: the USB cable uses differential mode signaling, which means that a USB transmitter sends the same data out on two cables, with inverted polarity (one cable will always reach max voltage when the other reaches min). The advantage of differential signaling is that it is very tolerant to noise, because any incoming noise will offset the voltage in both cables by the same amount in the same "direction", leaving the difference between the two voltages unchanged. The receiver will start by subtracting one voltage from the other by some (typically analog) means, which produces a value that is almost independent of the noise that may have been added along the way. (Assuming x is the noise voltage, imagine that one cable is showing "+1+x", the other "-1+x", so subtracting the two yields 1+x-(-1+x)=1+x+1-x=2 -- notice that x conveniently disappeared from the result.)


    The differential signal is also less prone to "escaping" or radiating out from the cable, as the two data cables will emit RF signals that cancel each other out almost perfectly.


    Unfortunately USB devices are prone to adding a noise signal to the USB signal, which is the same on both data cables. This noise is called a "common mode" signal (as it is common on both cables). The common mode signal can easily escape from the USB cable, which isn't shielded too heavily and behaves like a nice antenna, and the escaping RF signal can cause interference in other devices.


    So this is where the "can" (ferrite bead, or in EE parlance "common mode choke") comes in. When the cable is looped around a ferrite donut, the common-mode signal will induce a magnetic field in the ferrite that attenuates the common mode signal (typically equivalent to around 100 ohms of impedance). The ferrite will have much less of an effect on the differential signal, because the two induced fields from the two cables will cancel each other out. So in short, any signal that is in phase on the two cables will be greatly reduced, while the differential signal will pass through mostly unharmed. Most PCs will have a choke in the USB signal path right before the USB connectors to fulfill the regulatory requirements on how much RF noise they can emit. But in handheld devices it may be more cost effective to skip the internal choke and just bundle a cable that has a choke just "outside" the usb connector.


    Based on Intel's USB platform design guidelines document, a choke will actually degrade the USB signal a little bit. This means that the fancy cables may actually result in a poorer data signal. It should be noted though that the USB signaling is very robust, and any approved cable will have a low distortion that approved USB devices can easily tolerate.


    Should I clip magnets on my cables? The short answer is "no". The longer answer is "only if you know precisely what you're doing".


    First of all, clipping something on the cable will do nothing. If the cable just passes through the center of a ferrite ring you will see no effect. You have to loop the cable around a ferrite ring (either inside or outside of the "can") to get noticeable results. (see this PDF, which is the data sheet of the "can" that is used on the first USB cable that I came across on my desk).


    Secondly, if you use the wrong type/size of ferrite, it can interfere significantly with the signal you are trying to feed through the cable, especially if that signal isn't actually differential. In this case, the ferrite will behave as if you just cut your cable and soldered a bunch of 100..1000 ohm resistors into the signal path.


    In conclusion, unless you are experiencing interference issues in your home, you can safely ignore the presence or absence of ferrite beads on your cable and live happily ever after...

  7. Currently deployed to Okinawa, all the Caches here are WGS 84, and there are absolutely no problems with any GPS, I use a 60csx, some of my guys have Explorist, Etrexs, etc. There are no maps in my GPS, but if you have it programed or have software your square.


    I assume you know that you can download free Garmin maps for Japan. I'm not sure about the coverage on Okinawa, but major cities are actually pretty good. It proved to be very useful when I was visiting Tokyo...



  8. Can you be 100% sure it is 2.8 version ?

    I would be extremely surprised that in the production line at the time they made this GPS, they had these soft release. Most come with older release than available on the Garmin web site.


    This is true for almost any equipment. Consider the time it takes from the factory in Taiwan or China to the final customer !


    Actually, my Venture cx got shipped about a week before the v2.5 software for that unit came out. And it already had the new release. This means that either Garmin packages the units in the US and updates them all; or that the factory starts using the new firmware weeks before they are published on the website.

  9. I ordered my upgrade to Navigator 8 from City Select 7 last night. The new DVD will be shipped but I think we are going to have to pay the $75 upgrade fee when we instal the software. Anyone else know about this?

    Thanks guys!


    Depends on when you activated your CS7. If it was after May this year, you'll probably get a free ride. Otherwise you'll have to pay.

  10. I too have an eMap that's 7+ old. It doesn't have the latest software version, doesn't pick up all the satellites, but except for heavy wet canopy, it puts me dead on the spot everytime. It's still in mint condition despite a few drops and bouncing around in the jeep.


    I guess we eMap owners should start a club. I too have an eMap from the golden ages of non-routing GPSes. It has an occasional contact issue with the screen cable (that developed the 50th time it fell off a dashboard), and there is a streak on the screen where it got wet (it took a swim sometime down the road), but otherwise it still works just fine. I hardly ever use it myself, but I often loan it to friends and family, and they usually return it with a story about how it saved their behinds.


    For the record, none of my (Nokia) cell phones have ever died on me either, and I usually end up replacing them after about 4 years because they turn obsolete. My brother goes through them on an annual cycle. So like others said, longevity depends on what you do with the unit as much as how well it is designed.

  11. It happens to be like this:


    There are four unknowns, X, Y, Z and time. To solve for these four values, you need four equations, in this case represented by satellites.


    If only three are available, then the GPS can manage anyway, by making the often fairly correct assumption that your elevation (Z) is the same as it was last time it was on. Thus only three unknowns remain to find.

    The fact that you often don't get any lock with three satellites, is that usually, the reason that you can get only three is that buildings or trees are obstructing the view of the sky. Hence, the satellites that still can be received, are probably pretty high on the sky, and grouped rather tight together, or perhaps more or less on a line. The latter often happens in a street, where there are high buildings, since you can only see a line of the sky.

    This kind of satellite arrangement will be so unfavorable, that the GPS will find the DOP value too high, and thus defer the positioning until it gets the distance from one more satellite. Then, it may actually be a 2D solution you get, in spite of having four satellites, since two of them may be too close to each other to be useful as anything but one single satellite.


    Great explanation! This is precisely what's going on.

    (Ok, one minor correction: GPSs operate in a Cartesian coordinate system where the origin is the center of Earth. So Z is technically not your elevation, but if you assume an elevation you can add another equation for X, Y and Z that restricts possible solutions.)

  12. I'd like to know if the 60CSX uses the static navigation as well.


    I read that one way it effects us is that if you stop then go slowly it won't show you moving for a time. I would assume you would notice delays in the compass arrow,etc. as well when you stop and go alot in your using the gpsr.


    They do that I guess so it keeps it jumping all over the place as the chipset is sensitive


    Yes, that is indeed the case. For car navigation, and in the case of the Sirf II chipset, it was a better compromise to sacrifice low-speed behavior to reduce jumpiness. In fact, many of the 60c(s)x owners complain about how the GPS "wanders" while they are standing still (but would also object to a loss of low-speed resolution, I'm sure :))


    In general the Sirf III is good enough that static navigation is not worth using; in fact hardly any manufacturer has it enabled by default.


    As for the 20 channel thing: the Sirf III is built on the principle of trying to grab as much signal data as possible, even if those signals are reflected or they don't fit with the current speed/position assumption, and then using a massively parallel calculation unit to try to figure out the most likely solution based on all that data. The "extra" channels that aren't actively tracking satellites are used to search for other potential signals that may it be doppler-shifted, reflected or coming from a barely visible satellite.

    The biggest benefit of the extra channels is realized during a cold start, where the GPS has to experiment a lot before it comes up with an initial speed/position/time assumption.

  13. Is there any software out there that will allow a PPC to run .mps files from mapsource?

    I have tried just taking a screenshot and using an image viewer but zooming makes it grainy (naturally)....


    Are you trying to display routes or waypoints something from an mps file, or are you trying to view the maps (.img files)?


    For the former task there are tons of software, as long as you convert your waypoints or tracks or routes or whatever to a more common format, like gpx.


    For the latter task, you can use GIS Russa (http://www.gisrussa.com/). I've used it in Japan with the free Japanese maps, and also with US topo maps, and it works OK. It lacks some pretty fundamental features, but it does a good job of showing your location and track over the map. If you already have the maps, it's definitely worth the $30 registration fee.


    If you are just looking for basic/topo maps, the other choice is to get a software like memory map (http://www.memory-map.com/) or back country navigator (http://www.backcountrynavigator.com/), and purchase/download/scan/build the state-level 24k topo DVDs, or individual 24k segments. This approach will be more expensive and/or labor intensive though (but it does get you 24k topomaps for any area you wish, and not just the sucky Garmin topo maps).

  14. I am new to all this....but could someone please explain what is 1:100,000 and 1:24,000 terms mean? I am lost...i don't know much about it


    The 24k maps would have much more detail of the area than the 100k ones. If you download USAPhotoMaps, switch it to topo mode (T) then fill the screen (F), you will see the 24k map. If you scroll out to about 64 meters/pixel, the downloaded map will disappear. If press F again, you will get the 100k equivalent.

    The difference is quite substantial, as you will see...

  15. Also, according to Garmin's comparison page, the Venture Cx doesn't have the Tide Prediction utility, which may or may not be important to you.


    I think that must be a typo there, because the software of the Venture Cx and the Legend Cx is exactly the same, and even their user's manual is the same (it says "Legend Cx and Venture Cx" on the cover page).


    The only significant difference is the color of the box. Some like yellow, some not so much.


    The card that comes with the Legend Cx is way too tiny to be usable for anything, so the original poster should expect to buy a new one regardless of which unit he picks.

  16. Also, if you will be doing a lot of driving with the GPS, you will be better off with one that does voice guidance (text-to-speech is more annoying than useful, but basic spoken "turn left, turn right" style instructions are a godsent).


    I apologize for replying to myself. I wanted to add one more thought:


    Before I actually had a GPS that could do voice navigation, I always thought that it would be a waste of money and not very useful. Now I can't imagine life without it (much like I can't imagine traveling without a GPS, or surviving without a cellphone -- both of which I was somehow able to do for decades in the distant past). So if you do go down the 60cs route, do not, under any circumstances try a higher-end model beforehand, or you may become spoiled.


    The Quest would be a pretty decent compromise if it had the sirf-iii chipset (or in case you live out in the middle of the desert where thick foliage and tall buildings will be the exception rather than the rule).

  17. It seems as if the Garming 60CS is one of the best to get for Geocaching and it will also work in the car.


    Where are you going to be car navigating and/or geocaching? If it's a big city for the former (with tall buildings), or a forest for the latter, you will really-really want a sirf-iii unit (such as the cx). Also, if you will be doing a lot of driving with the GPS, you will be better off with one that does voice guidance (text-to-speech is more annoying than useful, but basic spoken "turn left, turn right" style instructions are a godsent).


    So all in all, imho the 60cs will work for both, but will be far from ideal for either. I had a 60cs for a few years, and honestly I wouldn't again spend a single cent on the crappy compass and altimeter in the "s" versions.


    For what it's worth, I now have a PDA phone with a bluetooth GPS for car navigation and hiking, and a Venture cx for the occasional case when a PDA is really not suitable.

  18. Sticking with the Palm will seriously limit your choices (essentially to Mapopolis). Mapopolis isn't bad, but if you had a PPC, it wouldn't be my first choice. As far as car navigation, I would say that Mapopolis is slightly better than the 60cx. The biggest advantage is that your PDA will give you voice guidance, so you don't have to distract yourself from driving by looking at the screen (the 60cx will only beep, and you have to read what it wants off of the screen). I have literally driven across the US with an eMap and 60cs, and they were both very useful. However, if I was given a chance, I would choose a PPC for car navigation without hesitation, because it has voice guidance, it calculates better routes, it calculates much faster, and it's much-much easier to enter addresses or find POIs. I currently have a Vista Cx and a PPC PDA Phone with a Holux 236 GPS, and unless there are special circumstances (no power for 10+ hours, wet conditions, rough conditions), I use the PPC for both hiking and driving.


    As for choosing between wires and bluetooth: I would vote for bluetooth. Wired will give you all sorts of complications, and you will have to get a different set of cables if you want to upgrade your PPC. The only drawback of bluetooth is that you need an additional power source for the GPS (or you need to keep its battery charged). But I guess that most wired solutions will also require external power unless your PDA can be a USB host.


    As others have mentioned, if you get a Sirf III unit (may it be a dedicated handheld GPS such as the 60cx or just a bluetooth receiver), it will probably work just find behind your windshield and give you great reception (see http://www.gpspassion.com/fr/articles.asp?id=143&page=4 , http://www.gpspassion.com/fr/articles.asp?id=175&page=3).

  19. When using Garmin Mapsource to load a topo map onto my GPSmap 60 I recieve this error:


    There is a problem with this GARMIN application.


    Error Information:


    At: 8/15/2006 9:06:29 PM (UTC)

    OS: Windows XP Service Pack 2

    Processor: Intel Processor Level: 15, RAM: 1047280 KB


    C:\DOCUME~1\BRYANM~1.KEL\LOCALS~1\Temp\Rar$EX00.266\Garmin Topo Disks\East\05623488.img


    It only happens when I try to load a map. I have no problems with waypoints or routes. Any help would be appriciated. I have already tried uninstalling and reinstalling with no luck.


    You may want to go into the registry and delete the HKLM/Garmin and HCKU/Garmin subtree then reinstall from scratch. And before you do, extract the disks from the rar file properly.

  20. Have you tried GPS Visualizer? (excuse me, this is a website and not a download but it apparently does what your looking for).


    It has to work on the road without a connection (download the maps home, then go out driving the terrain). Thanks for the tip, tho.

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