[aprssig] GPS problems in Los Angeles?

[Stephen H. Smith]

On 5/21/2011 9:40 AM, Alex Carver wrote
> I was driving up I-210 starting at the junction of I-210 and CA-134 (entered the highway just north of Colorado Blvd.)
>

Considering that Colorado runs parallel to the 210 for about 5 miles through 
most of Pasadena (about 3 blocks south of the 210) this doesn't say much....


> I also happened to see a related problem (loss of satellite lock) in Burbank in the Empire Center parking lot.

There is a string of 1.9 GHz PCS cell sites right by the side of the freeway, 
along this stretch of the 210 through Pasadena and Glendale,  that can overload 
and block 1575 MHz GPS receivers for about a 1/4-mile radius around each 
site.   I have observed effects along this stretch ever since PCS came online 
in the early 1990s.   Newer receivers with higher-dynamic-range front ends 
don't seem to suffer as much as the older ones.

In downtown commercial districts, a combination of PCS overload and multipath 
reflections from   metalized-glass  solar-reflective  high-e  windows on modern 
all-glass office buildings can make GPS go nuts for a block or two.    I have 
seen this effect both in downtown L.A. and in suburban monuments to the cubicle 
culture like Walnut Creek, Irvine, Torrance, San Jose, etc that are dotted with 
numerous glass office buildings and corporate headquarters.

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