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A 6 channel GPS receiver from 1993

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Re: A 6 channel GPS receiver from 1993

#71

Post by matheusmoreira »

rtkgps wrote: post #63

So cool to see how the technology has evolved over the years, now we can achieve accuracies down to one centimeter with GPS. Check out what Emlid has been building in this space. http://emlid.com

Centimeter precision still requires a base station. Gotta leave a GPS receiver stationary for days so it can average out the errors and compute its own position precisely. With that accurate receiver it's possible to correct the measurements of other receivers nearby up to some maximum range.

This requires raw GNSS measurement data support which is not available in most consumer units and is an incredibly proprietary mess in the professional surveying equipment space. It was actually Google who improved the status quo by mandating pseudorange support in Android.

Re: A 6 channel GPS receiver from 1993

#72

Post by mceachen »

aziaziazi wrote: post #52
TedDoesntTalk wrote: post #18

The original GPS receivers in the late 80s and early 90s did not have maps. And they used LCD screens. The one I owned by Lowrance required 6 AA batteries. Not AAA. Not rechargeable. Optional power through a cigarette-auto cable, but that's not helpful when on foot. It burned through batteries like crazy. I owned this one: https://web.archive.org/web/20231104153749/http://retro-gps.... (Lowrance GlobalNav Sport) 160…

Wondering why « No rechargeable » ? I recall rechargeable AAs in late 90, didn’t they exist in early 80 ?

Nickel cadmium AA batteries (what was available in the 90s) were not great. They self-drained to flat after a month, and had "charge cycle memory," so if you discharged them a couple times to, say, 60%, that became the cell capacity. Even fully charged, they only put out 1.2v.

Nickel metal hydride, and specifically Eneloops, were a game changer, as their self-discharge was only 10%/month, and had virtually no charge cycle memory.

Re: A 6 channel GPS receiver from 1993

#73

Post by GuB-42 »

23B1 wrote: post #69
GuB-42 wrote: post #16

Earlier quoted context omitted.

If sharing useful tech is betrayal, I wish there would be more traitors. On both sides.

Tell me you're too young to remember the cold war without telling me ;-)

I am 41, so, old enough to remember the end of the cold war as a child. I was almost exactly 10 at the fall of the USSR.

But, maybe most importantly, I am not from the US nor Russia, I am French. And while we were on clearly the western side, we had a somewhat more nuanced view of the conflict, I mean, we even had (and still have) a communist party.

Re: A 6 channel GPS receiver from 1993

#74

Post by wutwutwat »

spookthesunset wrote: post #43
callalex wrote: post #31

Earlier quoted context omitted.

Also kids these days don’t know the pain of GPS taking 3-10 minutes to get a position fix without almanac data.

Back then even light tree cover would sometimes trash the signal enough to lose position. While modern GPS can get a position fix pretty quick, a cold start on standalone units can still take a while before it discovers enough satellites. The crazy thing to me is now days my little tiny watch can do Wifi, Several Bluetooth protocols, 5G, NFC, Wireless charging and probably some other stuff I'm forgetting about. Oh an…

> While modern GPS can get a position fix pretty quick

Can they? I have popular usb gps receivers and it still takes many minutes to get a lock on enough satellites to give accurate positioning. Given that it is dependent on things flying overhead in space, I don't think the receivers are where any "boot speed/signal lock" improvements can happen.

Mobile phones are no exception, they've just employed several tactics to make the perception seem as if it's instant.

They start with "course" location which is based of the geo data of the cell's ip address and vicinity to known wifi access ssids. They also know where you were at when the phone went into standby or was powered down, and can reasonably assume you haven't gone far away from that location without the accelerometer noticing movement of any kind (keep in mind most phones do not fully shutdown even when powered off). That's all a very good and pretty accurate starting point for when you fire up maps on your phone, and by the time it is a problem a "fine" gps signal is locked. And usually due to other system services (like network config, find my device, etc) firing up gps when you unlock your phone or some other privacy invading app running gps as a background task, there's usually a fine grained gps lock by the time you even open your maps app.

Re: A 6 channel GPS receiver from 1993

#75

Post by Libcat99 »

hexmiles wrote: post #54
aziaziazi wrote: post #52

Earlier quoted context omitted.

Wondering why « No rechargeable » ? I recall rechargeable AAs in late 90, didn’t they exist in early 80 ?

Not OP, but i remember having a camera that use AAs and would not support rechargeable. While it powered up, it would not take photos and instead shutdown. I think they used to be able to deliver less power, also when i put them in the gameboy the little led was a tad dimmer that non rechargeable one even when fully charged

Most of the old rechargeable aa or aaa batteries were NiCd, which would be 1.2V vs the 1.5 you get from alkaline. I believe the voltage drops off more slowly than alkaline, but since the starting voltage is lower some devices just can't handle it.

We had a set of cb radios when I was a kid, they had 12 aa battery spaces but two "blanks" installed. You used the blanks and 10 batteries for alkaline, but removed the blanks and installed 12 if using rechargeable to bring the voltage to an acceptable level.

Re: A 6 channel GPS receiver from 1993

#76

Post by RecycledEle »

ljf wrote: post #57
aziaziazi wrote: post #52

Earlier quoted context omitted.

Wondering why « No rechargeable » ? I recall rechargeable AAs in late 90, didn’t they exist in early 80 ?

Even in the early 90s my good rechargeable batteries (AA) only put out 1.2v when freshly charged and dropped lower than that as they ran. They also ran far shorter than duracell or similar expensive batteries. So one the voltage may have been too low and two the usable loge might have been too short for these power hungry devices

True.

Many 1980's electronic devices needed too much power to be run by the NiCd batteries of that era.

I failed to learn DC motors, controllers, and gear boxes in part because I lacked batteries powerful enough to drive the small motors I had. (Or maybe I was an idiot:o) Decades later, lithium 18650 cells make it easy for my students.

Re: A 6 channel GPS receiver from 1993

#77

Post by RecycledEle »

IIRC, there were ambulance-shaped advertising gimmicks given away that looked like functional GPS receivers, but did not function for some reason. I never figured out if all the chips on them were bad or if just some of the chips were bad.

I would not assume that GPS receiver was ever designed to work. It may have been just for looks despite having a lot of expensive parts on it.

Re: A 6 channel GPS receiver from 1993

#78

Post by makomk »

wutwutwat wrote: post #74
spookthesunset wrote: post #43

Earlier quoted context omitted.

Back then even light tree cover would sometimes trash the signal enough to lose position. While modern GPS can get a position fix pretty quick, a cold start on standalone units can still take a while before it discovers enough satellites. The crazy thing to me is now days my little tiny watch can do Wifi, Several Bluetooth protocols, 5G, NFC, Wireless charging and probably some other stuff I'm forgetting about. Oh an…

> While modern GPS can get a position fix pretty quick Can they? I have popular usb gps receivers and it still takes many minutes to get a lock on enough satellites to give accurate positioning. Given that it is dependent on things flying overhead in space, I don't think the receivers are where any "boot speed/signal lock" improvements can happen. Mobile phones are no exception, they've just employed several tactics…

Modern GPS receivers are much faster. They can search for every possible satellite at every offset rapidly in parallel, meaning that they don't need the almanac in order to get a GPS lock quickly. They do still need the orbital data for each satellite being used, but that's transmitted by the satellite itself much more regularly than the almanac and mobile phones can generally speed things up even further by downloading a small amount of assistance data that contains orbits for all the satellites for the next day or so.

Re: A 6 channel GPS receiver from 1993

#79

Post by wutwutwat »

makomk wrote: post #78
wutwutwat wrote: post #74

Earlier quoted context omitted.

> While modern GPS can get a position fix pretty quick Can they? I have popular usb gps receivers and it still takes many minutes to get a lock on enough satellites to give accurate positioning. Given that it is dependent on things flying overhead in space, I don't think the receivers are where any "boot speed/signal lock" improvements can happen. Mobile phones are no exception, they've just employed several tactics…

Modern GPS receivers are much faster. They can search for every possible satellite at every offset rapidly in parallel, meaning that they don't need the almanac in order to get a GPS lock quickly. They do still need the orbital data for each satellite being used, but that's transmitted by the satellite itself much more regularly than the almanac and mobile phones can generally speed things up even further by download…

TIL, thanks!
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