Foliage Attenuation Study

[N_Jay]

Isn't "Foliage Attenuation" just another name for multipath induced fading? :lol:

Kinda like what happens to GPS...

No! All three are very different.
1) Foliage attenuation is reduction of signal principally due to the water held within foliage
2) Multipath Fading (Typically Log-normal fading or Rayleigh fading)
3) Satellite usually deal with Rician fading and Doppler Spread

 

[poltergeisty]

So foliage attenuation could play a factor on GPS accuracy? I noticed my old GPS 12 could not get a 3D situation in the forest. Only 2D I.E lat and long, no Alt.

 

[slicerwizard]

So foliage attenuation could play a factor on GPS accuracy?

Why not? Anything that attenuates/blocks 1.57542 GHz will impair GPS performance. Were there any tree trunks or big branches present?

I noticed my old GPS 12 could not get a 3D situation in the forest. Only 2D I.E lat and long, no Alt.

It didn't see enough satellites; 3 for 2D, 4+ for 3D.

 

[N_Jay]

So foliage attenuation could play a factor on GPS accuracy? I noticed my old GPS 12 could not get a 3D situation in the forest. Only 2D I.E lat and long, no Alt.

But that was not what you said.

Yes, it could be attenuation in the forest. It could also be crappy sensitivity, or a poorly orientated antenna.

 

[SCPD]

When you combine tree foliage with steep topography in mountains (narrow canyons) GPS works quite poorly. If there are satellites overhead the angles are close to parallel and the position given is very inaccurate. I've been in some canyons when there isn't a satellite overhead, resulting in no reception at all. These canyons are not the small box type canyon variety where it is obvious GPS won't work, but in fairly wide but have ridges in the 1000 to 2000 feet above the valley floor.

In the mountains depending solely on GPS is not a very good idea. Batteries can fail, cold temperatures can affect performance, and good reception is often not available. I always carry a compass, maps, and the knowledge to use them.

 

[N_Jay]

. . always carry a compass, maps, and the knowledge to use them.

Hmmm, maybe we don't want poltergeisty to find his way back??:twisted:

 

[poltergeisty]

It didn't see enough satellites; 3 for 2D, 4+ for 3D.

I know that... I was in a forest! :lol: Was wondering if foliage attenuation is a considerable factor on GPS.

Yes, it could be attenuation in the forest. It could also be crappy sensitivity, or a poorly orientated antenna.

This GPS is remarkably pretty accurate, despite not benefiting from any form of augmentation.

In the mountains depending solely on GPS is not a very good idea. Batteries can fail, cold temperatures can affect performance, and good reception is often not available. I always carry a compass, maps, and the knowledge to use them.

No doubt. I know how to read a topographic map...studied that to no end in ROTC. I have a Silva compass. I am a survivor... the sun and stars can guide me too :lol:

...besides, I can read aeronautical maps, STAR and DP plates... :lol:

 

[N_Jay]

I know that... I was in a forest! :lol: Was wondering if foliage attenuation is a considerable factor on GPS.

You have to wonder?

This GPS is remarkably pretty accurate, despite not benefiting from any form of augmentation.

Sensitivity and accuracy are two different attributes.

No doubt. I know how to read a topographic map...studied that to no end in ROTC. I have a Silva compass. I am a survivor... the sun and stars can guide me too :lol:

We can always hope.

...besides, I can read aeronautical maps, STAR and DP plates... :lol:

Damn!

 

[DaveH]

Isn't "Foliage Attenuation" just another name for multipath induced fading? :lol:

Kinda like what happens to GPS...

No, they are completely unrelated. Mutipath has to do with reinforcement or
cancellation (partial or complete) of radio waves over different paths, such as
reflected v. direct. Foliage loss is just that, the effect of a lossy dielectric.

.....

Actually, they may be somewhat related, if some of the sources or multipath
are affected by foliage loss and others are not, but they are different mechanisms.

Dave

 

[SCPD]

No doubt. I know how to read a topographic map...studied that to no end in ROTC. I have a Silva compass. I am a survivor... the sun and stars can guide me too :lol:

...besides, I can read aeronautical maps, STAR and DP plates... :lol:

The Silva Ranger is their most expensive model if I remember correctly. Its advantage is a sighting mirror used to line up distant objects while reading the azimuth on the face of the compass. The mirror can be used in a pinch to flash aircraft and people (rescue types) who might be trying to locate you.

I bought my first one in college (Northern Arizona University School of Forestry) and used it throughout my career. We were really drilled in map reading and making; pacing; and compass work. After awhile you gain some "dead reckoning" skills and can just "feel" in your feet where you are. On a 7.5 minute topo I could usually tell within the width of a pencil line what my location was when hiking all day cross country. This is one reason I don't care for using a GPS. The other is the lousy map software (proprietorial) that comes with most GPS units. Until I can load about 10 USGS 7.5 minute topos into the unit without the use of proprietorial software I'm not really interested in buying a new one. I would like to have small memory cards I could plug in that contain additional topos of my choosing. I could then have plenty of maps with me on a long (100+ mile) backpacking trip.

The old GPS I have is sort of a toy and I use it to estimate my ETA to my destinations when traveling, if the route I'm traveling is fairly straight and my destination lines up with my route of travel. It also does a fair job of verifying a speedometer.

 

[poltergeisty]

I can understand the awareness aspect you gained. My former teacher was a Green Beret in Vietnam and pretty much said the same thing.

This GPS doesn't have the fancy map stuff.Personally don't care for that sort of thing. Yes, they do make great speedometers! :lol:

You have to wonder!

A feeling of puzzlement or doubt is the definition.. :lol: