Doppler vehicle ground speed detection?

Google Hotwheels radar gun

Reply to
cs_posting
Loading thread data ...

That's easy. The speed of the elephant is the same as the average speed of the four tortoises.

--
Grant Edwards                   grante             Yow! I smell like a wet
                                  at               reducing clinic on Columbus
 Click to see the full signature
Reply to
Grant Edwards

Was it not Four elephants and One turtle?

--
avast! Antivirus: Outbound message clean.
Virus Database (VPS): 000753-0, 01/07/2007
 Click to see the full signature
Reply to
Allen

Yes, but will it take off?

formatting link

martin

Reply to
martin griffith

It depends on where you heard the story. In some verions it's one elephant standing on one turtle standing on... The version I remember most vividly was a drawing of was an elephant with a each foot on a tortoise.

Whatever. Just average the speeds of whatever's at the bottom...

--
Grant Edwards                   grante             Yow! MMM-MM!!  So THIS is
                                  at               BIO-NEBULATION!
 Click to see the full signature
Reply to
Grant Edwards

Both are needed. Air speed and ground speed.

If you need to travel from A to B eg 100 KMS and there is a 100Kt head wind how much fuel do you need? How long will it take to get to B?

BTW as the head/tail winds change in flight it is a fun calculation.

Several US Air crews died when the hit the Jet stream and over shot the airfield in N Africa by several 100 miles. They were not found until decades later by chance.

--
\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
\/\/\/\/\ Chris Hills  Staffs  England     /\/\/\/\/
 Click to see the full signature
Reply to
Chris Hills

Depends on what you want, airspeed indicated, airspeed compensated for barometric and temp effects, Mach number, or groundspeed.

For light planes, measuring ram air pressure in the undisturbed airflow and converting to indicated airspeed is generally good enough. The resulting number is needed more for impending stall notification and structural limitations than for navigation. Groundspeed is useless for these issues.

For navigation, nearly everyone has a GPS that will provide true groundspeed.

Reply to
Jim Stewart

It's more complicated than that. Ignoring Mach effects, aircraft fly on what's usually called "Indicated Air Speed", which is what your,

*ahem*, airspeed indicator indicates. As you mentioned, this is usually measured by comparing the ambient static pressure with that of the air flowing into a forward facing pitot tube. In essence it's how hard the relative breeze is beating against the front of the aircraft. The relationship between indicated air speed and your true airspeed is severely dependant on the local air pressure, which varies with altitude, temperature and weather.

But as I mention aircraft fly on indicated airspeed. So an aircraft flying at 100kts IAS, will handle the same (have the same flying characteristics) at sea level or at 20,000ft, but will have a true airspeed at sea level of 100kts, but 146kts at 20kft. In short, flying at high altitude gets you more "true" airspeed for a given amount of work, which is why everyone likes to fly at altitude. For example, an airliner at 35kft will cover *twice* as much ground (assuming no wind) for the same amount of fuel as it would at sea level.

It's the *true* airspeed (vector) that you can then add to the wind speed (vector) to get your groundspeed, not your IAS.

Reply to
robertwessel2

covered under radar :)

--
Marriage is a wonderful institution, but who would want to live in an 
institution.
 Click to see the full signature
Reply to
El Chippy

of

plain

You stayed awake through your ground school lessons and remember what was said!

I knew that turbojets gain quite a bit in fuel economy by going higher, but I didn't realize it is 2:1. Of course, those of us whose personal aircraft's service ceiling is well below the flight levels aren't concerned about the fuel usage of the turbojets.

BTW: Present-day diesel-electric locomotives have a radar-based mechanism to measure speed for use in detecting and avoiding drive wheel slippage. The mechanism has to be quite robust to operate in a very harsh environment.

Reply to
Everett M. Greene

Yeah, something like that... ;-)

It's not just jets, all aircraft benefit from the thinner air up in the flight levels. It's just that most propeller driven aircraft are limited to lower altitudes for different reasons (engine power, crew oxygen). The Tu-95 ("Bear") is a good counter example, and regularly flies in the upper 300s. Even more ordinary piston singles do much better up high, which is most obvious for the turbocharged versions, where they retain enough engine power to actually fly up there. Of course that usually comes with the annoyance of a rubber tube up your nose, but...

And does that have a direct link to the sand dispenser gadget?

Reply to
robertwessel2

... snip ...

In the old days this was dead easy. The engine went "choo ... choo ... choo choo choo", unmistakably indicating slippage :-)

--
 
 
 Click to see the full signature
Reply to
CBFalconer

I was watching a video shot in the cab of a steam engine where the engineer was having trouble with slick rails. He was constantly "sawing" on the throttle -- open the throttle until the wheels slipped, close the throttle, open the throttle... He was earning his pay.

Reply to
Everett M. Greene

Believe it or not, so do farm tractors set up for "precision agriculture". The on-board navigation equipment needs a better estimate of ground speed than you can get from counting drivetrain RPMs.

-- Dave Tweed

Reply to
David Tweed

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.