OEM GPS Boards - Sensitivity Level Comparisons

**edikp** · 02-17-2005, 05:00 PM

Talks in this thread: OEM GPS Modules. have inspired me to do a research on the sensitivity levels of OEM GPS boards. I'd like to share what I've researched so far. Some notes:

This research is done entirely through the utilization of the Internet by browsing the specification sheets of different GPS boards produced by different manufacturers
This is not to be mistaken with an exhaustive side-by-side lab tests
The information is laid out as follows: manufacturer, model, sensitivity in dBm (if available), sensitivity in dBW, tracking or acquisition sensitivity type (if available)

So here's the list:

Garmin (www.garmin.com)
- GPS25LV: -165dBW
- GPS15LV/LH: -165dBW
GlobalSat (www.globalsat.com.tw)
- ET102: -170dBW
- ET202: -170dBW
- ET301: -175dBW
- ET401: -159dBm = -189dBW
Laipac (www.laipac.com)
- TF-10: -175dBW
Qinetiq (www.qinetiq.com)
- Q20:
  - -185dBW (tracking)
  - -180dBW (acquisition)
u-blox (www.ublox.com)
- TIM-LH:
  - -158dBm = -188dBW (tracking)
  - -152dBm = -182dBW (acquisition)
- TIM-LR (this is the engine on the SBR-LS board):
  - -149dBm = -179dBW (tracking)
  - -140dBm = -170dBW (acquisition)

Hopefully you've noticed, some boards are more sensitive than others. If we take TIM-LH which is among the ones with the most sensitivity levels, is designed for indoor GPS, urban canyons & dense foliage, covert applications, etc. I had planned to purchase the combination of u-blox TIM-LR and Murata gyroscope for Dead Reckoning (DR). I have since changed my mind to purchase the TIM-LH instead due to the more complex in-vehicle mounting requirements of the DR (interface to external sensors such as speed pulse/wheel tick, etc.)

Please add to this list other boards' sensitivity levels. Also, if you are researching DR, please share your research if you would. Maybe we can compare notes.

**0l33l** · 02-21-2005, 02:47 PM

How much is it costing you? Will you get fast lock times?

**jcdillin** · 02-21-2005, 03:07 PM

fast lock times? my gps 15LV goes from power on to a 6 to 7 sat lock in about 4 seconds, goes to 11 to 12 sat lock in about 10 seconds. Which in turn means I have gps fix even before my computer comes out of hibernation.

**0l33l** · 02-21-2005, 03:11 PM

Originally Posted by jcdillin

fast lock times? my gps 15LV goes from power on to a 6 to 7 sat lock in about 4 seconds, goes to 11 to 12 sat lock in about 10 seconds. Which in turn means I have gps fix even before my computer comes out of hibernation.

So, how do you know that the computer has locked on to the sats if you can't see the status of them because the computer is resuming from hibernation? Does your garmin have dead reckoning?

**edikp** · 02-21-2005, 04:06 PM

@0l33l: Currently I'm still using the Garmin GPS25LV. The specification sheet says that it takes 15 seconds when all data is known. It has an internal memory powered by a rechargable battery that maintains the memory of the last postion prior to its main power supply being shut down.

In all actuality though, by the time my computer comes out of hibernation (less than 10 seconds) I'm already getting a locked position. I care less about how many satellites the GPS receiver is actually receiving. Just as long as it has got a locked position and is able to relay that information to my navigaion software that I'm good to go.

**0l33l** · 02-21-2005, 04:42 PM

This makes me want to get rid of my earthmate

I have a plan of doing a speedometer based on GPS, so dead reckoning would be vital. The garmin unit unfortunately doesn't have it

**edikp** · 02-21-2005, 04:59 PM

None of Garmin's OEM boards, you are right. You can always buy the 2660, though.

Although at the beginning of the thread I've mentioned that I'm buying u-blox's TIM-LH, I'm back to weighing my decision between it and the SBR-LS (TIM-LR) with gyro module. I'm still wondering: sure the TIM-LH is sensitive but how sensitive is it exactly? If I'm in a multi-floor parking building, will it still be getting and able to interpret the signals?

On the other hand: how accurate or close to accurate will the SBR-LS actually be?

Most of it I guess depends on whether I want to go ahead and plunge my self to buying and testing it. Also, time to do the research seems to be scarce nowadays.

**0l33l** · 02-21-2005, 05:05 PM

Originally Posted by edikp

None of Garmin's OEM boards, you are right. You can always buy the 2660, though.

Although at the beginning of the thread I've mentioned that I'm buying u-blox's TIM-LH, I'm back to weighing my decision between it and the SBR-LS (TIM-LR) with gyro module. I'm still wondering: sure the TIM-LH is sensitive but how sensitive is it exactly? If I'm in a multi-floor parking building, will it still be getting and able to interpret the signals?

On the other hand: how accurate or close to accurate will the SBR-LS actually be?

Most of it I guess depends on whether I want to go ahead and plunge my self to buying and testing it. Also, time to do the research seems to be scarce nowadays.

I'd love to see someone do this and test it out. The modle is also SiRF compatable, right?

**IntellaWorks** · 02-21-2005, 05:18 PM

Garmin's 15h/l have an internal battery that can last up to 21 days, it maintains a lock even when your computer is off...

**edikp** · 02-21-2005, 05:25 PM

Edited: Oops, intellaworks' respond sneaked in. This is the respond to 0l33l's last question.

I'm kinda waiting for updates by hklomann from the mentioned thread link above. Hopefully he continues to be forward and willing in sharing his information.

Which model? If you meant the TIM-LR & TIM-LH then they support: NMEA, UBX (u-blox's proprietary), and RTCM (FCC & US Coast Guard standard, according to www.rtcm.org).