Jump to content

Garmin Handheld Sensitivity?


Kohavis

Recommended Posts

I found this fact a little disturbing - The handheld GPS manufacturers don't publish the sensitivity specs for their handhelds. It's the same for Garmin, Lowrance, DeLorme, etc. I've even downloaded the manuals and SDK guides and foraged in the appendices for this bit of information. No luck.

 

They use subjective terms like "High sensitivity" and give accuracy specs in meters, with and without WAAS. But the "specifications" sections on their websites don't list the most important spec of all - how well it acquires a signal :huh:

 

I'm an engineer and I feel uncomfortable, and even suspicious when there is a glaring oversight like that made :)

 

Other GPS products make this information openly known. For example - the $41 Navisys GR-300 SiRF III USB GPS Dongle for a laptop:

 

# Technical Data:

# SiRF III, 20 channel, L1 frequency, C/A code

# Accuracy: <2.5m (Autonomous); <2m (WAAS); (50% 24hr static, -130dBm)

# TTFF (Hot/Warm/Cold): <1 sec / <35 sec / < 42 sec

# Sensitivity: -142dBm (acquisition); -159dBm (tracking)

# Update Frequency: 1Hz

# Protocol: NMEA V3.00, 4800bps, GGA, GSA, GSV, RMC, VTG

# Power: 5V, 50mA

 

Beautiful. Thank you! That tells me everything I need to know about the receiver. And this wasn't even at the manufacturer's website. This was at Semsons.com - an online vendor. It's in the description of the unit.

http://www.semsons.com/nagrusbgpsdo.html

 

How can I make an accurate comparison of different models, aside from the "gee whiz" bells and whistles, if I'm not provided with the cold, hard facts about how it performs?

 

I'm new to geocaching, and maybe I'm missing something obvious. How did everyone else here pick their model? Am I making too much of this?

Link to comment

I picked the model I have, the Garmin Vista HCx, because it had the newer "High Sensitivity" receiver that outperforms the Vista C I used prior to that. I also chose Garmin because of their reputation for excellent Customer Service.

 

I also picked the Vista HCx because I could use it for auto-routing, with the excellent Garmin City Navigator maps installed on it. It is also a nice small size for hiking.

 

I'm sure others will give their reasons for choosing the models they have.

Link to comment

Beautiful. Thank you! That tells me everything I need to know about the receiver.

 

I'm new to geocaching, and maybe I'm missing something obvious. How did everyone else here pick their model? Am I making too much of this?

That does not tell you everything you need to know about a GPS receiver. (It may be good enough for an analog radio.)The processing of the signals is very important. Some units will seem to bounce their position around when you are still. This makes for inaccurate tracks, and difficult position determination.

 

Does the unit use the best of 4 satellites for a 3d position? Or does it process more than 4 for an "over-determined solution." Does it use averaging when stopped moving? Does it filter out reflected signals (multi-path)? Sometimes too sensitive without good processing is bad.

The companies usually do not tell us these things.

 

For geocaching, people usually choose one of the latest generation models based on the features they like. If you are using your unit mostly for other purposes, such as track generation, or photo tagging, your choice may be different.

Link to comment

I love specs too but I much prefer getting real world feedback from users on equipment. I've used countless products that were beautiful on paper and feeble in practice. If Garmin says something is high sensitivity, they probably mean it; if it's a no-name closeout at Big-5, then be skeptical.

Link to comment

I found this fact a little disturbing - The handheld GPS manufacturers don't publish the sensitivity specs for their handhelds. It's the same for Garmin, Lowrance, DeLorme, etc. I've even downloaded the manuals and SDK guides and foraged in the appendices for this bit of information. No luck.

 

They use subjective terms like "High sensitivity" and give accuracy specs in meters, with and without WAAS. But the "specifications" sections on their websites don't list the most important spec of all - how well it acquires a signal :huh:

 

I'm an engineer and I feel uncomfortable, and even suspicious when there is a glaring oversight like that made :)

 

Other GPS products make this information openly known. For example - the $41 Navisys GR-300 SiRF III USB GPS Dongle for a laptop:

 

# Technical Data:

# SiRF III, 20 channel, L1 frequency, C/A code

# Accuracy: <2.5m (Autonomous); <2m (WAAS); (50% 24hr static, -130dBm)

# TTFF (Hot/Warm/Cold): <1 sec / <35 sec / < 42 sec

# Sensitivity: -142dBm (acquisition); -159dBm (tracking)

# Update Frequency: 1Hz

# Protocol: NMEA V3.00, 4800bps, GGA, GSA, GSV, RMC, VTG

# Power: 5V, 50mA

 

Beautiful. Thank you! That tells me everything I need to know about the receiver. And this wasn't even at the manufacturer's website. This was at Semsons.com - an online vendor. It's in the description of the unit.

http://www.semsons.com/nagrusbgpsdo.html

 

How can I make an accurate comparison of different models, aside from the "gee whiz" bells and whistles, if I'm not provided with the cold, hard facts about how it performs?

 

I'm new to geocaching, and maybe I'm missing something obvious. How did everyone else here pick their model? Am I making too much of this?

 

You're very observant. I have owned about 10 Garmin units and have been most disappointed in the latest two units they have released (Oregon and Colorado). They are hyped as High Sensitivity Receivers, but they seem more prone to drift than earlier units (60scx) that do not have High Sensitivity chipsets.

 

There is also the speed at which they update which seems to be slower than earlier units , that results in speed and distance (odometer) errors.

 

Finally, many people blame some of their inaccuracy on the fact that they are "high sensitivity" receivers and hence are prone to errors that "low sensitivity" chipsets are not prone to.

 

So these units are not all they are hyped to be. They do have more robust Geocaching features that appeals to the average reader on GS.

 

All that being said and given that I've blasted the Oregon and Colorado many times, I just went out and bought another Oregon 400T :)

Edited by schmidtbaby
Link to comment
found this fact a little disturbing - The handheld GPS manufacturers don't publish the sensitivity specs for their handhelds. It's the same for Garmin, Lowrance, DeLorme, etc. I've even downloaded the manuals and SDK guides and foraged in the appendices for this bit of information. No luck.

You piqued my curiosity, because I thought I had seen *something* about sensitivity on the Delorme PN-20.

 

The only thing I came across was this mention in the specifications page at the back of the PN-20 Users Manual (I downloaded the manual and searched on dBm, turned up on page 78, Appendix B ):

Weak signal tracking down to -145dBm

Is that what you were looking for? I'll grant you that's not very easy to find. The manual is downloadable as a pdf from the website, but a search on "dBm" on the Delorme website returns no hits. You appeared willing to do the download, so I'm not sure how you missed it...it *is* a bit of a needle in the haystack.

 

I also have to say that for me, it's a pretty meaningless number...as in over my head. Your Mileage Apparently Does Vary.

Edited by embra
Link to comment

I'll admit I have an engineer's mindset. I love specs, and I dislike it when they're left out, for whatever reason. Call me a geek - I've been called much worse :)

 

I love specs too but I much prefer getting real world feedback from users on equipment.
So do I. I'm using the specs as a starting point, not a finishing point. I would never base a purchase solely on the stated receiver sensitivity. Real-world use always wins out over paper performance.

 

But, that said, it would be handy to see a correlation between receiver sensitivity and user satisfaction, if there even is one. More information is always good, never bad :D

 

That does not tell you everything you need to know about a GPS receiver.
First of all, thank you for replying. I appreciate it.

 

I think you misunderstood, though. I was referring to the actual receiver within the handheld unit, not the overall unit. Strictly speaking, a receiver is a circuit that receives a signal, applies AGC if needed, then passes it along to the next stage. In the electronics world, it's not an accurate description to call a handheld a "receiver" because a complete handheld has an antenna, a receiver, a signal processing stage, a storage subsystem and memory, an overall microprocessor/controller, a display subsystem, and a power subsystem. My fault - I already knew that "GPS Receiver" is the term used for the entire handheld. I apologize for the confusion.

 

Does the unit use the best of 4 satellites for a 3d position? Or does it process more than 4 for an "over-determined solution." Does it use averaging when stopped moving? Does it filter out reflected signals (multi-path)?
Those are not "receiver" specs, strictly speaking. They're overall GPS handheld specs that reflect design features of the signal processor and the overall unit control logic. Again, my fault for confusing the issue.

 

The reason I focused on the receiver (strict sense of the word) sensitivity is because that is the starting point. Without good sensitivity, you have nothing else, since it can't process what it doesn't have to begin with :)

 

I'm not slamming any particular brand. I've heard a lot of good things about certain models of all 3 brands. I'm just trying to sort it all out. It's mind-boggling to see the variety of hardware out there. And most of it is so inexpensive, too. I remember the early GPS days when you had to spend a fortune for a single-channel, big, bulky unit, and it wasn't even portable like a handheld. You had to lash a big serial GPS mouse to your laptop :blink:

 

@embra - Thanks for finding that. I did Garmin first, then Lowrance, then De Lorme. I admit by the time I got to De Lorme, I saw a pattern and was starting to skim a bit. A bad habit. I must have overlooked that spec. While it's not a full sensitivity spec, it's a lot more useful than nothing. It at least gives a comparison point.

 

@Miragee - Thank you. Now that's the kind of recommendation I would look for after narrowing down my list a little. It's user feedback that will ultimately help me determine which one to buy :D

 

Thanks, all. You guys are great! B)B)

Link to comment
You're very observant. I have owned about 10 Garmin units and have been most disappointed in the latest two units they have released (Oregon and Colorado). They are hyped as High Sensitivity Receivers, but they seem more prone to drift than earlier units (60scx) that do not have High Sensitivity chipsets.

 

Just a Minor nitpick--the 60CSx does have the High Sensitivity SiRFStar III.

 

I'm an engineer and I feel uncomfortable, and even suspicious when there is a glaring oversight like that made

 

I thought this was an interesting quote. I am not a engineer (nor do I play one on TV), and the sensitivity information you posted may as well have been written in Chinese. These are essentially consumer grade products--and most consumers don't know what those numbers mean either.

 

I have had 3 Garmins the first one was an eMap that I bought at a store closing sale for around $80. About the only feature I was familiar with was the fact that it would display a map. As I upgraded (60CS, 60CSx) I stayed with Garmin because I was familiar with the way the operate and liked their features--autorouting, bright display, and ease of use. Sensitivity was important (one of the reasons I upgraded for 60CS to 60CSx) but it was not a something that I compared numerically. It was more like I read reviews and comments on this board of people reporting they could hold a signal in tough conditions--tree cover, inside buildings, and in urban settings.

Link to comment

<snip>

You're very observant. I have owned about 10 Garmin units and have been most disappointed in the latest two units they have released (Oregon and Colorado). They are hyped as High Sensitivity Receivers, but they seem more prone to drift than earlier units (60scx) that do not have High Sensitivity chipsets.

Actually, the 60CSx has a high-sensitivity chipset (Sirf Star III). It was the first Garmin handheld to have one, and people have been frustrated by Garmin's seeming inability to surpass or (in some cases) even match the performance of that receiver in later handhelds.

Link to comment

<snip>

You're very observant. I have owned about 10 Garmin units and have been most disappointed in the latest two units they have released (Oregon and Colorado). They are hyped as High Sensitivity Receivers, but they seem more prone to drift than earlier units (60scx) that do not have High Sensitivity chipsets.

Actually, the 60CSx has a high-sensitivity chipset (Sirf Star III). It was the first Garmin handheld to have one, and people have been frustrated by Garmin's seeming inability to surpass or (in some cases) even match the performance of that receiver in later handhelds.

 

I stand corrected on the 60scx. As I understand it, the Sirfstar's are more expensive than the chipsets Garmin is now using?

Link to comment

<snip>

You're very observant. I have owned about 10 Garmin units and have been most disappointed in the latest two units they have released (Oregon and Colorado). They are hyped as High Sensitivity Receivers, but they seem more prone to drift than earlier units (60scx) that do not have High Sensitivity chipsets.

Actually, the 60CSx has a high-sensitivity chipset (Sirf Star III). It was the first Garmin handheld to have one, and people have been frustrated by Garmin's seeming inability to surpass or (in some cases) even match the performance of that receiver in later handhelds.

 

I stand corrected on the 60scx. As I understand it, the Sirfstar's are more expensive than the chipsets Garmin is now using?

 

That is my understanding, but I do not know that for certain.

Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...