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  #211  
Old March 19th 17, 04:33 PM posted to rec.bicycles.tech
AMuzi
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Posts: 9,032
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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


Ads
  #212  
Old March 19th 17, 04:34 PM posted to rec.bicycles.tech
Joerg[_2_]
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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/
  #213  
Old March 19th 17, 04:56 PM posted to rec.bicycles.tech
SMS
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Posts: 7,997
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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.
  #214  
Old March 19th 17, 06:24 PM posted to rec.bicycles.tech
Frank Krygowski[_4_]
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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&sectionNum= 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
  #215  
Old March 19th 17, 06:29 PM posted to rec.bicycles.tech
Jeff Liebermann
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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
  #216  
Old March 19th 17, 11:01 PM posted to rec.bicycles.tech
Jeff Liebermann
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Posts: 2,569
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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
  #217  
Old March 20th 17, 01:48 AM posted to rec.bicycles.tech
John B.[_3_]
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Posts: 3,563
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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.

  #218  
Old March 20th 17, 03:59 AM posted to rec.bicycles.tech
Jeff Liebermann
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Posts: 2,569
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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
  #219  
Old March 20th 17, 06:25 AM posted to rec.bicycles.tech
John B.[_3_]
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Posts: 3,563
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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.

  #220  
Old March 20th 17, 07:59 AM posted to rec.bicycles.tech
Jeff Liebermann
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Posts: 2,569
Default More About Lights

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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