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More About Lights
On 3/18/2017 9:47 PM, Jeff Liebermann wrote:
On Sat, 18 Mar 2017 15:11:56 -0400, Frank Krygowski wrote: On 3/18/2017 2:29 PM, Jeff Liebermann wrote: On Wed, 15 Mar 2017 14:08:44 -0400, Frank Krygowski wrote: Thing is, nobody's demonstrated any need for so much stationary "be seen" light, beyond the usual "well, it _could_ happen" safety inflation mentality. True, but you're thinking like engineering, not marketing. I do have too strong of a tendency to do that. See http://dilbert.com/strip/2014-12-18 That has a place of honor on our refrigerator door. I can see that this discussion is going to be all uphill. I'll be merciful and uncharacteristically brief. I worked for a company run by engineers that dug a hole for itself and then jump in by doing very little market research and ignoring their own marketing people. Designing a working product is only part of the puzzle. Packaging, merchandising, and selling it in a manner that customers will want to buy it is far more difficult because it's NOT an exact science like engineering. This is one reason that engineers fail to appreciate marketeers. It works the other way, where engineers are pathological incapable of letting go of their design and will continue to "improve" the design long after the customer has left and gone elsewhere. Incidentally, having one foot in each swamp, I had the dubious honor of being called a traitor by both sides. I really didn't appreciate the problem until that happened. Also, I tend to identify with Dilbert's PHB (pointy hair boss), partly because I've lost enough hair to look like him, but also because I can see myself in similar situations. Being in the middle between engineering, marketing, sales, and production is not my idea of fun job. I did it for a while running my father's company and hated it. Drivel: https://trackmaven.com/blog/national-days-calendar/ Hmmm... Today (Mar 18) is "National Supreme Sacrifice Day". I wonder if they mean human sacrifice? Quoting the great Peter Drucker, "Nothing gets done until somebody sells something." All the excellence of your design is for nothing unless you can pay the bills and earn a profit. -- Andrew Muzi www.yellowjersey.org/ Open every day since 1 April, 1971 |
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More About Lights
On 2017-03-18 11:00, Jeff Liebermann wrote:
On Fri, 17 Mar 2017 17:03:19 -0700, Joerg wrote: However, every time I asked dirt bikers who venture out into the sticks in Nevada they said that they tried their smart phones but that it really doesn't work well without a Garmin or other native GPS device. I've had the same experience when I try to run the GPS in "airplane mode". The GPS uses location data from the cell sites (AGPS) to improve its E911 accuracy and shorten acquisition time. Turn off the cellular part of the phone, or try to use GPS in an area where there are no cell sites is a problem. "Using an Android GPS in Airplane Mode" http://backcountrynavigator.com/using-android-gps-airplane-mode/ There are also issues with the antenna. Size matters and the bigger patch antennas used in handheld GPS receivers offers much better sensitivity and view of the sky. I have a collection of about 10 assorted GPS receivers. Occasionally, I do a comparison of performance in challenging areas (hills, mountains, trees, indoors, underground garages, highly reflective environments, RF polluted environments, etc). If I have a nearby cell site to use as a starting or reference point, my Moto G smartphone does quite well. My Samsung S6, not so well but good enough. However, if I go into "airplane mode" to save battery power, performance sucks. The main problem is that without the position sanity check provided by AGPS, the smartphone GPS will produce wildly erratic positions caused by reflections, often miles away from my actual location. Some of the handheld mapping GPS receivers do the same thing, but not as badly. Miles is bad. That means a position indication is useless for any serious trail riding. Are at least the maps and the satellite view as good as on a PC? As long as it buffers enough before going off-grid that would help because I can fix my position pretty well via the use of landmarks. Good old triangulation. There is also some mapping trickery involved when using maps and AGPS. In order to improve (or fake) accuracy for E911, mapping smartphone apps like to round off positions to coincide with a roadway. It's a fair assumption that someone using a GPS map program would be on some kind of road. That's great, until you ride off the road and your GPS tracker thinks you're still on the roadway. So far, it hasn't been a problem. With me that's a problem because my favorite routes are off-road. I try to avoid raods whenever possible for many reasons. Like the one yesterday where a driver came very close and leaned on the horn in an attempt to push me from the lane to the side. No danger because he had slowed down to my pace but such low-lifes with a drivers license are annoying. And dangerous, especially when they are soused or nowadays high on whatever. You really need to get with the program and buy yourself an iPhone 7+, Only over my dead body :-) I'll resist the temptation to say something clever about your destructive testing methods. I wore out the BB on my road bike. Again :-( But it was 40 miles of fun (except for the road part) -- Regards, Joerg http://www.analogconsultants.com/ |
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More About Lights
On 3/19/2017 8:33 AM, AMuzi wrote:
snip Quoting the great Peter Drucker, "Nothing gets done until somebody sells something." All the excellence of your design is for nothing unless you can pay the bills and earn a profit. Yet there are some that design stuff and give away the designs out of the goodness of their hearts. Look at all the open-source software. Look at all the people that design stuff because they like to do it, not as part of their regular jobs. |
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More About Lights
On 3/19/2017 5:06 AM, Sir Ridesalot wrote:
On Sunday, March 19, 2017 at 12:34:21 AM UTC-4, Frank Krygowski wrote: On 3/18/2017 10:23 PM, Jeff Liebermann wrote: On Sat, 18 Mar 2017 19:52:02 -0400, Frank Krygowski wrote: And BTW, I think reflectors on pedals or cranks are extremely conspicuous. I'd be more in favor of mandating them than mandating taillights. Reflectors are already required in California: http://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=VEH§ionNum= 21201 21201(d) (1) A lamp emitting a white light that, while the bicycle is in motion, illuminates the highway, sidewalk, or bikeway in front of the bicyclist and is visible from a distance of 300 feet in front and from the sides of the bicycle. (2) A red reflector or a solid or flashing red light with a built-in reflector on the rear that shall be visible from a distance of 500 feet to the rear when directly in front of lawful upper beams of headlamps on a motor vehicle. (3) A white or yellow reflector on each pedal, shoe, or ankle visible from the front and rear of the bicycle from a distance of 200 feet. (4) A white or yellow reflector on each side forward of the center of the bicycle, and a white or red reflector on each side to the rear of the center of the bicycle, except that bicycles that are equipped with reflectorized tires on the front and the rear need not be equipped with these side reflectors. I think most states are similar. But note the phrase "while the bicycle is in motion." -- - Frank Krygowski I don't know about you people butt... When I'm stopped at an intersection at night I like to have a light shining forward as well as a rear red light so that vehicles approaching me and turning can see there is something in front of them. Ditto for when just staarting from a stop and not yet up to soeed. that seems to be a time when there are a lot of cars that will turn infront of a bicyclist because the driver didn't see the bicyclist. A bicyclist can also be hidden from an approaching and or approaching and turning driver, by the headlights of a car or truck behind the bicyclist. You guys can go ahead and play Russian Roulette with cars at intersections at night because you have no working light giving forthlight from your bicycle there. I'll keep my light ON at those intersections so that other road users can see a bicycle is there. I like to have some reflectors on my bike. I also like to have a handlebar bag, a full-sized frame pump, fenders and other items. But I won't claim you're playing "Russian Roulette" if you make different choices - especially if I lack decent data. -- - Frank Krygowski |
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More About Lights
On Sun, 19 Mar 2017 08:34:51 -0700, Joerg
wrote: Miles is bad. That means a position indication is useless for any serious trail riding. Not exactly. It depends on what you're doing. If you try to plot your ride, you might get some screwed up data points mixed in with the data. For example, my last hike into the bottom of a local canyon yielded a maximum altitude of 3,000 feet higher than the ground. There was only one or two bad data points, but it was enough to screw up all the statistics. Same with maximum speeds traveled, where the distance covered between a real position indication and a bogus point or two is high enough for me to claim breaking the sound barrier. Mapping software authors know about all this and do their best to compensate. The most common and best method is to do a sanity check on all positions. If the GPS suddenly claims you've instantly moved many miles, that point gets dropped. You probably won't see garbage data on your smartphone or mapping GPS because of this feature. You will see garbage if you use raw NMEA-183 data in some application. If you want to see if you have a potential problem, just connect a data logger to the GPS and collect some $GPGLL sentences. Write a program that looks for large changes in adjacent sentences. The glitches, if present, should be drastic and obvious. Somewhere in my mess is a Windoze program that takes this data and provide both graphical and tabular accuracy statistics. I used to use it when we had to deal with selective availability. It's kinda neat. You park yourself in a highly reflective location (bottom of a rock canyon) and record about 30 mins of position data. Position excursions on the display are obvious. I use it for averaging readings over a long period in order to obtain better accuracy. Are at least the maps and the satellite view as good as on a PC? As long as it buffers enough before going off-grid that would help because I can fix my position pretty well via the use of landmarks. Good old triangulation. I'm not sure. Everything depends on the antenna sensitivity and bandwidth. There's a huge difference in performance between an antenna that uses a choke ring to reduce ground reflections as on survey receivers: https://en.wikipedia.org/wiki/Choke_ring_antenna and a smartphone that uses a tiny ceramic patch antenna. These articles cover the problem quite nicely: https://www.u-blox.com/sites/default/files/products/documents/GPS-Antenna_AppNote_%28GPS-X-08014%29.pdf?utm_source=en%2Fimages%2Fdownloads%2F Product_Docs%2FGPS_Antennas_ApplicationNote%28GPS-X-08014%29.pdf http://www.taoglas.com/wp-content/uploads/2015/07/Internal-GPS-Active-Patch-AntennaAPN-13-8-002.B.pdf Hmmm... probably more than you want to know. Suffice to say that the smaller the antenna, the narrower the usable bandwidth. This is important because small antennas work very badly with WAAS and barely can handle the L1/L2 bands. Gain also suffers. From the Taoglas article: Typical peak gain for GPS patch antennas on standardized ground planes are as follows: 25mm Patch 5 dBi 18mm Patch 2 dBi 15mm Patch 1 dBi 12mm Patch 0.5 dBi 10mm Patch -2 dBi By comparison to what's found in a smartphone, these patch antennas are HUGE. I can't seem to find the smartphone GPS antenna vendor, but as I vaguely recall, the typical gain was about -8dBi with a rather narrow view of the sky. Anyway, back to your question... If you look at the antenna, and assume that the receivers are all rather similar, your performance will be almost totally dependent on the GPS antenna. With me that's a problem because my favorite routes are off-road. I try to avoid raods whenever possible for many reasons. Like the one yesterday where a driver came very close and leaned on the horn in an attempt to push me from the lane to the side. No danger because he had slowed down to my pace but such low-lifes with a drivers license are annoying. And dangerous, especially when they are soused or nowadays high on whatever. Well, you could weaponize your bicycle to act as a deterrent. https://www.google.com/search?q=bicycle+gun&tbm=isch I wore out the BB on my road bike. Again :-( But it was 40 miles of fun (except for the road part) Sigh. At least you wore it out and didn't break it. Out of curiosity, what wore out? Bearings? Raceway? Seals? Mechanical doping motor? -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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More About Lights
On Sun, 19 Mar 2017 10:29:45 -0700, Jeff Liebermann
wrote: Somewhere in my mess is a Windoze program that takes this data and provide both graphical and tabular accuracy statistics. I used to use it when we had to deal with selective availability. It's kinda neat. You park yourself in a highly reflective location (bottom of a rock canyon) and record about 30 mins of position data. Position excursions on the display are obvious. I use it for averaging readings over a long period in order to obtain better accuracy. Foundit. Visual GPS: http://www.visualgps.net/#visualgps-content It's free and old but works nicely. Visual GPS XP works somewhat better, but costs $10: http://www.visualgps.net/#visualgpsxp-content New, improved, and free is Visual GPS View: http://www.visualgps.net/#visualgpsview-content All these will graphically show any radical excursions in position. I have several battery powered, BlueGoof GPS receivers. They're quite convenient for testing with VisualGPS. However, I prefer to use an RS232 data logger, which works on any GPS. After collecting data for maybe 30 minutes, I dump the output into the Visual GPS program and inspect the resulting mess. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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More About Lights
On Sun, 19 Mar 2017 10:29:45 -0700, Jeff Liebermann
wrote: On Sun, 19 Mar 2017 08:34:51 -0700, Joerg wrote: Miles is bad. That means a position indication is useless for any serious trail riding. Not exactly. It depends on what you're doing. If you try to plot your ride, you might get some screwed up data points mixed in with the data. For example, my last hike into the bottom of a local canyon yielded a maximum altitude of 3,000 feet higher than the ground. There was only one or two bad data points, but it was enough to screw up all the statistics. Same with maximum speeds traveled, where the distance covered between a real position indication and a bogus point or two is high enough for me to claim breaking the sound barrier. Mapping software authors know about all this and do their best to compensate. The most common and best method is to do a sanity check on all positions. If the GPS suddenly claims you've instantly moved many miles, that point gets dropped. You probably won't see garbage data on your smartphone or mapping GPS because of this feature. You will see garbage if you use raw NMEA-183 data in some application. If you want to see if you have a potential problem, just connect a data logger to the GPS and collect some $GPGLL sentences. Write a program that looks for large changes in adjacent sentences. The glitches, if present, should be drastic and obvious. I know nothing of U.S. mapping but I can assure you that using marine charts there is a definite problem, in some cases, in comparing GPS positions with existing charts. One of my friends favorite anchorages, in the S. Philippines, is on dry land according to the current marine chart of the area :-) To the extent that some, perhaps many, charts include offset information for use with GPS. -- Cheers, John B. |
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More About Lights
On Mon, 20 Mar 2017 07:48:44 +0700, John B.
wrote: I know nothing of U.S. mapping but I can assure you that using marine charts there is a definite problem, in some cases, in comparing GPS positions with existing charts. One of my friends favorite anchorages, in the S. Philippines, is on dry land according to the current marine chart of the area :-) To the extent that some, perhaps many, charts include offset information for use with GPS. There are plenty of ways to screw up a map. The most common is to use the wrong datum. WGS84 is the most common for GPS. However many countries have their own. For example, the USGS maps are still NAD27 and are sloooooowly converting over to NAD83. At one time Google Maps and Google Earth used the wrong datum for Santa Cruz CA and managed to shift the entire city to the east by 200 ft. That wasn't fatal for land navigation, but allegedly caused a problem when some fisherman tried to navigate his way into Santa Cruz yacht harbor in the fog and missed by 200ft. Looks like the Philippines uses PRS92 datum. http://georepository.com/datum_6683/Philippine-Reference-System-1992.html There is also the Luzon Datum of 1911: https://en.wikipedia.org/wiki/Luzon_Datum_of_1911 There are also various zones in the Philippines to be considered: http://tool-online.com/index/systemes-coordonnees/philippines.html My guess(tm) is that you'll find that the GPS is set for one datum (probably WGS84), while the printed map is based on PRS92 or earlier. The document mentioned in the above Wikipedia page footnotes, "Status of the geodetic infrastructure of the Philippines" looks interesting and will probably have come clues on conversions and errors. However, the link doesn't work. Looks like some tools are available: https://www.google.com/search?q=convert+prs92+to+wgs84 Looks like the difference is -128 meters E-W and -67 meters NS. http://georepository.com/transformation_15708/PRS92-to-WGS-84-1.html That's plenty of room to put your friends anchorage on dry land. There are other sources of error, but this is the most likely. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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On Sun, 19 Mar 2017 19:59:50 -0700, Jeff Liebermann
wrote: On Mon, 20 Mar 2017 07:48:44 +0700, John B. wrote: I know nothing of U.S. mapping but I can assure you that using marine charts there is a definite problem, in some cases, in comparing GPS positions with existing charts. One of my friends favorite anchorages, in the S. Philippines, is on dry land according to the current marine chart of the area :-) To the extent that some, perhaps many, charts include offset information for use with GPS. There are plenty of ways to screw up a map. The most common is to use the wrong datum. WGS84 is the most common for GPS. However many countries have their own. For example, the USGS maps are still NAD27 and are sloooooowly converting over to NAD83. At one time Google Maps and Google Earth used the wrong datum for Santa Cruz CA and managed to shift the entire city to the east by 200 ft. That wasn't fatal for land navigation, but allegedly caused a problem when some fisherman tried to navigate his way into Santa Cruz yacht harbor in the fog and missed by 200ft. Looks like the Philippines uses PRS92 datum. http://georepository.com/datum_6683/Philippine-Reference-System-1992.html There is also the Luzon Datum of 1911: https://en.wikipedia.org/wiki/Luzon_Datum_of_1911 There are also various zones in the Philippines to be considered: http://tool-online.com/index/systemes-coordonnees/philippines.html My guess(tm) is that you'll find that the GPS is set for one datum (probably WGS84), while the printed map is based on PRS92 or earlier. The document mentioned in the above Wikipedia page footnotes, "Status of the geodetic infrastructure of the Philippines" looks interesting and will probably have come clues on conversions and errors. However, the link doesn't work. Looks like some tools are available: https://www.google.com/search?q=convert+prs92+to+wgs84 Looks like the difference is -128 meters E-W and -67 meters NS. http://georepository.com/transformation_15708/PRS92-to-WGS-84-1.html That's plenty of room to put your friends anchorage on dry land. There are other sources of error, but this is the most likely. The marine GPS' that I've used were all WGS84. Generally speaking those who sail outside the U.S., are using British Admiralty charts, or copies there of. I used to buy Thai charts from the Thai Navy and they were based on Admiralty charts. I don't remember but I think that they were not WGS84. But datum aside, I had a copy of a chart of an island in the S. Pacific and the notes stated, it was based on surveys made by the HMS something or another, in 1790-something. I always thought that if I ever got onto the S. Pacific that I would approach those islands in the daylight with great care :-) -- Cheers, John B. |
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On Mon, 20 Mar 2017 12:25:07 +0700, John B.
wrote: The marine GPS' that I've used were all WGS84. Yep. That's the usual default setting. Generally speaking those who sail outside the U.S., are using British Admiralty charts, or copies there of. I used to buy Thai charts from the Thai Navy and they were based on Admiralty charts. I don't remember but I think that they were not WGS84. NOAA nautical maps use NAD83 (which is very close to WGS84). USGS uses NAD27 but is slowly moving to NAD83. Google Earth uses WGS84. Geocaching uses WGS84. Here's what the military thinks of "civilian" charts: http://msi.nga.mil/MSISiteContent/StaticFiles/Files/NautChrts_GPS_index.htm "Isolated datums, such as those used to position many islands in the Pacific Ocean, can be in error by a half mile or more (see figure). The datum shift to WGS 84 can be quite large, depending on the area of the world and the local datum in use." See the chart of Farallon De Pajaros Island, which requires a 1/2 nautical mile shift for the map to agree with GPS. http://msi.nga.mil/MSISiteContent/StaticFiles/Files/island.jpg But datum aside, I had a copy of a chart of an island in the S. Pacific and the notes stated, it was based on surveys made by the HMS something or another, in 1790-something. I always thought that if I ever got onto the S. Pacific that I would approach those islands in the daylight with great care :-) Possibly Captain James Cook, who went through the south pacific between 1768 to 1771. https://en.wikipedia.org/wiki/European_and_American_voyages_of_scientific_explor ation I have a nice Tamaya sextant, out of date HO 229/249 tables, and some charts. It's not very practical these days, but it does help one understand how such things work. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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