Urban Canyons and SirfIII

 

Just came back from a trip to downtown Chicago..My first experience with my c530 in a major city. Until now, I thought that SirfIII was the answer to the problem with reception in the city.
1. As I was walking down the street, the car icon kept jumping around from street to street and the unit kept recalulating.
2. Standing outside, on the th floor of a building with a clear view to the sky (day was cloudy), My unit could not find satellites and kept going to the "are you inside prompt".

Haven't seen much discussion of this lately.

BTW, traveled for 4 days and when I came back, it took me several hours just to read all the new postings. (So, how much time am I losing on a daily basis?)

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Garmin StreetPilot c530, Mapsource

no problem in NYC

While walking around NYC, signal and operation seemed normal. I did lose reception one time but only for a few seconds somewhere in the area of the NYSE building.
Didn't notice any jumping around of the car icon.

I came back to 11 days of unread posts...only recently have I caught up.

Hope your trip was a plesant one.

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........Garmin StreetPilot c550 / Nüvi 765...........

interesting - local factors?

Cant say I've had my Nuvi 350 in Chi-town, but in both Denver and Wash DC (obviously less tall bldgs) I've had very few issues ---- once it locked on. It definitely took longer than it does here in NC, and didnt like being among the buildings, under an overhang (but with some sky visible). Point 1 ad 2 were both walking - but was all of that out of your car?

SIRFIII is clearly better, but we always have room for improvement smile

Worst Cities

My biggest problem areas were in Boston and Pittsburgh. Boston is obvious but I couldn't figure out Pittsburgh. Must have been all the changes of elevation there.
I have never had any problems in Downtown Chicago with the exception of one area around Dearborn and Jackson Street. It was only once and I'm down there quite often when I'm home.

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******************Garmin Nüvi 1300T****************Member 6523*******************

Hope the new SiRFDiRect will

Hope the new SiRFDiRect will solve some of the problems.

http://www.sirf.com/PressRoom/Press.aspx?PressId=129

yes

photomatt wrote:

Cant say I've had my Nuvi 350 in Chi-town, but in both Denver and Wash DC (obviously less tall bldgs) I've had very few issues ---- once it locked on. It definitely took longer than it does here in NC, and didnt like being among the buildings, under an overhang (but with some sky visible). Point 1 ad 2 were both walking - but was all of that out of your car?

SIRFIII is clearly better, but we always have room for improvement smile

Yes all walking around NYC, no car, taxi, bus.
P.S. Most of my walking is done out of my car...lol

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........Garmin StreetPilot c550 / Nüvi 765...........

yes, did not have a car

photomatt wrote:

Cant say I've had my Nuvi 350 in Chi-town, but in both Denver and Wash DC (obviously less tall bldgs) I've had very few issues ---- once it locked on. It definitely took longer than it does here in NC, and didnt like being among the buildings, under an overhang (but with some sky visible). Point 1 ad 2 were both walking - but was all of that out of your car?

SIRFIII is clearly better, but we always have room for improvement smile

Yes, I was walking and didn't have a car.
BTW, I was on a 7th floor terrace with a clear view of the sky when I couldn't get any fix. In that case, I was standing, not walking.

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Garmin StreetPilot c530, Mapsource

Multipathing?

Ein wrote:

Hope the new SiRFDiRect will solve some of the problems.

http://www.sirf.com/PressRoom/Press.aspx?PressId=129

I loved the "Forward-Looking Statements". Almost as good as "Legislative Directed Spending" = "Earmarking"

For mkahn: Did you have WAAS turn on? I think the major problem in urban canyons is that you are picking up multipaths. I don't know if SiRFDiRect will solve all the problems.

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Computers are useless. They can only give you answers. - Pablo Picasso (Bob - Garmin c530, eTrex Vista HCx)

WAAS was turned off.

[quote=Summermug

For mkahn: Did you have WAAS turn on? I think the major problem in urban canyons is that you are picking up multipaths. I don't know if SiRFDiRect will solve all the problems.

Thanks Summermug
Actually I thought about that and turned it off (back to Normal). It didn't change the results. Actually, I was surprised that it didn't work, but it isn't a big deal. Posted for info purposes only.

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Garmin StreetPilot c530, Mapsource

I noticed it takes a long

I noticed it takes a long time to get a fix in Manhattan. When I ride the train to GCT, the GPS is useless being underground for the end of the train ride. But once I have a fix in Manhattan my Nuvi 350 works very well.

You mentioned a 7th floor terrace? If it was not a roof terrace you only had at best half a clear sky. With those conditions you would probably have issues depending on the satellite geometry at the time.

You can click the upper left and get the satellite page and see the received satellite signals. Where you getting any satellites?

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eTrex Touch 35, Nuvi 1350LMT, Nuvi 350, Nuvi 260, Garmin GPS III, Basecamp

c530 doesn't show satellites

thetick wrote:

You mentioned a 7th floor terrace? If it was not a roof terrace you only had at best half a clear sky. With those conditions you would probably have issues depending on the satellite geometry at the time.

You can click the upper left and get the satellite page and see the received satellite signals. Where you getting any satellites?

The c530 doesn't have that option. It did show two red bars out of the 5 potential green. You are correct that I was backed by the building and only had a forward view of the sky. I did leave the GPSr on for about 15 minutes but it still said "tracking satellites".

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Garmin StreetPilot c530, Mapsource

Since you had 2 red bars

No Satellite page with the c530? OK.

Since you had 2 red bars then you did have some satellites and were close to getting a fix. By close I mean you probably only needed one more satellite. You probably just had bad geometry that day. Try it another day and you may get a fix.

No GPS can reliably get a fix with only a forward view of the sky. The geometry probability is against always getting a fix in this case.

I noticed in Mid-town on the 12th floor on Madison some days I get a fix in 5 minutes or less and other days I don't get any fix no matter how long.

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eTrex Touch 35, Nuvi 1350LMT, Nuvi 350, Nuvi 260, Garmin GPS III, Basecamp

Maps are still in:)

I had a similar issue in Philadelphia (3 tall buildings) where the unit just kept recalculating and running me around in circles. I then plugged in the external antenna but nothing changed. I had all the bars but very little guidance. I shut the unit off and restarted it, with the same results. I didn't trust it in map mode either.

I finally shut it off and pulled out the old paper map:)

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660, v3.80

Real Canyons

I took my iPAQ rx5915 that has the SiRF III receiver to Alaska on a cruise and used it on a drive out of Skagway. In the 2000+ foot canyons driving up to Canada on the Klondike Highway, the unit had a lock but showed the highway about 100 feet right of the centerline. Would have made an interesting drive. I suspect it might have been the map accuracy but might have been multipath giving an inaccurate position for the car since once up out of the canyons, it was dead on the road.