Alert distance on the Speed Cameras POI

http://www.poi-factory.com/node/41439

I'd read that string before, but upon reading it a second time I found the magic number: The Speed Camera POI alerts 36 seconds (regardless of your current speed) before the camera's location. Thanks.

Phil

For info from Poi Loader help.

Speed Information

Speed information can be included in the file name or in the names of individual POIs within the file.

POI Loader determines speed information based on the following information, listed from highest to lowest priority:

Speed information included in the name of the individual Custom POI. For example, a POI named "SpeedZone@30" will have an alert speed of 30 regardless of the speed information specified in Manual mode or in the file name.

Speed information entered in Manual mode.

Speed information included in the file name. POI Loader interprets any numbers in the file name as speed information.

Proximity Alert Information

Proximity alert information can be calculated automatically based on speed information. It can also be included in .gpx data files or added in Manual mode.

POI Loader determines proximity alert information based on the following criteria, listed from highest to lowest priority:

Proximity alert information listed for individual POIs in a .gpx file. This information overrides all other proximity alert information.

Proximity alert information entered in Manual mode.

Proximity alert distance calculated by POI Loader based on speed information in the file name or in individual POI names. This calculation uses the following formula:

Prompt Distance = 36 seconds * Speed.

A default proximity alert distance of 400 meters/0.25 miles if the file name contains the word "redlight."

If a file name contains a valid speed number or if all records in a file have speed encoded in the name, then all records in the file will include speed and proximity alerts. For example, a data file with the file name "Speed_30" generates speed alerts of 30 mph (or kph, depending on the type of units selected in POI Loader) for each POI in the file.

If the file name contains "redlight", POI Loader assumes all records in the file have proximity alerts with a distance of 400m/0.25 miles.

If a file contains "GATSO," "mobile," "SPECS," "safety," "speed," or "camera," but does not have a speed, POI Loader uses a default alert speed of 0, which means you will always be alerted. You can override this default value by entering the speed in Manual mode.

You can also enter speeds for each POI individually by adding the @ symbol and a number after the name of the POI. For example, a Custom POI named "Ridgeview@25" would create a POI named "Ridgeview" with a 25 mph speed alert.

Thank you for this info.

That is a common misconception but if you read carefully the statements in the POI Loader help file you can see why it is wrong.

The 36 seconds comes from this paragraph:
============================
“Proximity alert distance calculated by POI Loader based on speed information in the file name or in individual POI names. This calculation uses the following formula:

Prompt Distance = 36 seconds * Speed.”
=============================

The Speed Camera Poi have speed information in individual Poi names so:

Prompt distance is: 36 * (speed in Poi name)

Assuming the vehicle travels at the “current speed” for the Prompt Distance, the time it takes to travel the Prompt Distance at a “current speed” = Prompt Distance/(current speed )

Replaceing “Prompt Distance with “36*(speed in Poi name)” results in the following:

time = 36seconds*(speed in Poi name)/(current speed)

Thus if the speed in the Poi name is 40 and the current speed is 60 the time is: 36*40/60 = 24 seconds.

BTW a few years ago Gary Hayman wrote an article on his site based on my discussions with him about this speed – time topic:

http://home.comcast.net/~ghayman3/garmin.gps/pagepoi.08.htm

Having the audible warning has been quite beneficial at times, especially in unfamiliar areas. The warning is always long before any of the visible signs can be seen.

It would benefit the members if you compose this as a FAQ and include the example. It would be nice to have for a reference if the question comes up again.

Although the answer to plunder’s question “What is the alert distance for the Speed Camera POI file?” is included in my post above: “Prompt distance is: 36 * (speed in Poi name)” I think more detail may be needed by some to correctly calculate it.

Assuming that POI Loader has units of distance and speed set to Feet and MPH (Miles Per Hour) the equation would be:

Alert distance (in feet) = 36 seconds *(speed in Poi name)MPH *(88 feet/second)/(60MPH)

Which reduces to:

Alert distance (in feet) = 52.8*(speed in Poi name)

Good math.

I will work on it.

I use 600ft for the speed and red light cameras

only way you could use 600 feet for speed cameras is to eliminate the 'at' symbol and remove the word speed from the file. The default for the word speed is 1320 feet or 400 meters which POI Loader set because of the use of a key word.

I agree that one would have to eliminate the 'at' symbol but since speed information entered in the manual mode is of higher priority than speed information in the file name, one would not have to remove the word speed from the file name.

Also the default alert distance when the word speed is in the file name (and no number is present) is 1056 feet (0.2 miles) not 1320 feet (.25 miles). I have verified this by testing.

I also tested the keywords "GATSO", "mobile", "SPECS", "safety", and "camera" and they gave the same result as "speed".

I note that the only key word mentioned in the Poi Loader help that results in a 1320 feet (.25 mile) is “redlight”.

Thank you for the refresher on the POI Loader defaults. I would have sworn earlier versions of POI Loader were a 1/4 mile. 2^8 does seem like an odd value for a default equating to approximately 300 meters.

You brought up another point often overlooke, the hierarchy of settings. The highest priority or level is the manual setting overriding any other setting. The second level being the @ symbol followed by the file name or keyword.

For those not quite clear on this here's another example:
POI Loader in manual and the alert speed is set to 30.
All other speed data is ignored including numbers following an @ or in the file name.

A file has values preceeded by an @ but nothing set in manual mode. A repeating speed alert is triggered if the speed is above the value following the @ symbol.

A file name contains a number below 128. A speed alert is triggered for every entry if a manual speed has not been set or the @ symbol followed by a number is not present in an entry.

If you have set a speed alert, you will be notified with an alert before you reach the point however, if you are going faster than the alert value, the alert will repeat until you slow down to or below the alert value. If you are within the alert distance and stop the alert will repeat when you start moving again.

I assume that is a typo since 2^8 = 256 and that number does not seem to relate to the conversation - but I cannot figure what you may have meant.

Too complicated for me.....I guess I will just take the defaults from now on

I'm not certain at all if there's a simpler way to do this but my goal here will be to try and help you choose a specific distance in setting off both the redlight camera and speed camera file.

1- I have an old version of POI Loader, version number 2.5.4 which can be found here

http://gawisp.com/perry/garmin_uilities/

2- I have my main POI File and within that I have a lodging file, rest area file and a file which I name speed. In that speed file I have my redlight cameras along with speed cameras which I've downloaded from here.

3- Open the speed file using note pad, press edit, press replace, in the box find what put @ , in the box that says replace with leave it blank, press replace all, once all is done and you exit the program it will ask if you want to save changes and mark yes.

4- Using the POI loader go in the manual mode and set the distance you would like for both the redlight camera file along with the speed camera. I use 820 and 1657 feet but you can choose what best suits your needs & the jobs done

I was going to try to make 1056 an even power of 2 and lost count. 2^10 is 1024 and my brain wasn't functioning that early. But I have to admit that 1056 is a little odd as it's not an even amount in meters either (321.86).

Thanks Box Car – I see now what you were pondering and I fully understand how a slip like that can be made. Don’t ask me how I know.

As you well know, it may be folly to apply logic to what Garmin programmers do, but here are some of my thoughts:

I think they are working in decimal fractions of miles and kilometers.

For example, I believe that they chose the 36 seconds discussed above so that the alert distance comes in hundredths of a mile or kilometer. (One of the factors used in the conversions makes use of the fact that 1 hour = 3600 seconds.)

If one uses all the proper dimensions and conversion factors in the speed alert equation, alert distance = 36 seconds*(speed in Poi name), it can be shown that:

Alert distance (in miles) = (speed{in MPH} in Poi name)/100

Alert distance (in kilometers = (speed{in KPH} in Poi name)/100

Thus if speed is 40 MPH Alert distance = .4 miles

And if speed is 40 KPH Alert distance = .4 kilometers

====================
Now, as to the default alert distance when the keyword “speed” is in the csv file name, note that 1056 feet is 0.2 miles.

I think you will find that if you:

• Put “speed” and no numbers in a csv filename (and the Pois in the file contain no speed information)
• Put the Pois on your Garmin with POI Loader
• Disconnect and turn on your Garmin and set the Units to Miles in System
• Do a Where To -> Extras and select one of the Pois loaded in the above steps and you should see an alert distance of 0.2 mi.
• Go back to System and set Units to Kilometers
• Do a Where To -> Extras and select one of the Pois loaded in the above steps and you should see an alert distance of 0.4km.

Conclusion: If you put “speed” and no numbers in a csv filename, and the Pois in the file have no speed information, and then load the pois on your Garmin with Poi Loader the alert distance will be 0.2 mi if the Units in System is set to Miles and will be 0.4km if the Units in System is set to Kilometers.

Note: In the tests I ran this morning it did not seem to matter what the units were set to in POI Loader FOR THIS PARTICULAR CASE.

Sorry but I have to pull a Columbo on you and say that there is one more thing. Your statement:

is not entirely true although it is supported by the priority list under “Proximity Alert Information” in POI Loader Help.

Actually, the manual mode does not override “any other setting”. The speed data given by numbers following an @ in the name field of individual Pois inside a csv file cannot be overridden by the manual mode. The priority list under “Speed Information” correctly states:

I have confirmed this by loading the Speed-Cameras.csv POIs in manual mode and putting a speed in the “Default Alert Speed” text box.

I guess you might have been thinking in powers of 2 again (2^7 = 128) but the correct number is 125.