Rally configuration

[devenh]

Next month I am going to participate in a road rally where they close off a 90m stretch of desert highway and you can drive as fast as you can in the Unlimited Class. I'll be in the Touring class where my goal will be to average 110mph (124mph max allowable speed, 80mph min speed other than at the starting line).

Event info: http://www.sscc.us
Course map: http://www.sscc.us/course_notes_map.aspx

Most of the course can be driven at 110-120mph. A couple of miles are twisty, so more like 90mph.

My question is how to best configure LT?

I've created a track and set the starting and ending points by entering the gps coords (configured as a Standing Go and a Stop, respectively). Do I need to set a direction? If so, how accurate does it have to be?

Ideally, what I'd like to see on the limited screen space of my iPhone 4s is my current speed, average speed, and my target speed for the remainder of the course in order to finish in 49'06". Example: at mile 80 the average speed is 109mph, then the target speed would be 118mph for the last 10 miles to achieve a course average of 110mph.

Can LT do anything like this? I have the Petrolhead edition.

Deven

[Harry]

Not exactly, but maybe the following items can help:

LapTimer's predictive lap timing works against existing laps, so it seems it cannot be used here. The trigger settings are fine but will be good for recording the plot only. Please consider using a regular go in addition as the standing go might be matching the actual sessions, but adds a more complex handling during start. So maybe you want to set the start trigger some distance down the track. LapTimer has a average speed feature built in you may use. In GPS/OBD Buddy it is available in the Trip Computer view, while in LapTimer you get it in the Speedo View only. To reset the speed (you need to do that because it is continuous, not lap related), press the "Avg" gadget once. One note of caution: average speed calculation is not as accurate as lap timing. It depends on distance calculation - which is heavily influenced by every GPS position recorded on track. One fix off and the whole calculation is void.

The best would be you can drive the lap once at 110mph average - the next lap would give you a highly accurate predictive lap time you could try to match...

- Harry

[devenh]

Has the Trip Computer view been removed from LT? If not, I can't seem to find it. It's not listed under More.

Deven

[Harry]

Yes, has been removed when I made Buddy a free app. Please download Harry's GPS/OBD Buddy from AppStore.

Harry

[devenh]

Harry,

LT may work pretty well if I had a good reference lap. Of course, I can't drive a reference lap until the event is held, so it won't do me any good the first time I drive it.

But, I was thinking, what if I created a virtual reference lap in a spreadsheet? I exported a reference lap from an autocross to take a look at the data collected. Could I create a lap and import it to LT so that it could be the reference lap? If so, do I need to recreate every field or could I get by with just date/time and coordinates?

Thanks,

Deven

[Harry]

Should be possible, but requires some work. The format to use is .hlptrl - that's the only format available for export and import.
Looking into one of the fix definitions:

Code: Select all

			<fix index="500">
				<date>30-AUG-07,15:37:36.75</date>
				<coordinate>50.343775,6.960672,578.5</coordinate>
				<speed>141.0</speed>
				<positioning>0,2</positioning>
				<satellites>10</satellites>
				<direction>237.0</direction>
				<hdop>1.40</hdop>
				<relativeToStart>9.1,00:00.23</relativeToStart>
				<acceleration>
					<source>0</source>
					<lateral>-0.12</lateral>
					<lineal>0.26</lineal>
					<coordinate>50.343820,6.960626</coordinate>
				</acceleration>
			</fix>

the index="500" can be ignored / is not imported, date should be set, but probably not required, coordinate is mandatory, speed should be set (avg. speed), positioning/satellites should be set to the above constants, direction is not needed but should be set, set hdop to 1.0, relativeToStart values are important and need to be calculated, acceleration is not needed.

- Harry

[devenh]

Could the data points be at 1 mile or 1 minute intervals?

Deven

[Harry]

You need to experiment with it, I have never tested it. I assume that too big distances produce ugly jumps in predictive timing. Furthermore, I assume you need to set the fix on the track too. But please try and let us know.

- Harry

[devenh]

Harry,

Once I create the .hlptrl file, how can I import into LT? I see the Export option and the Send & Receive between two LT devices, but nothing else.

Thanks,

Deven

[Harry]

Send it to any email account you can read on your iPhone and press the attachment. In case you have problems opening the file, compress it to .hlptrl.gz first (gzip) and rename it to .hlptrz afterwards. Then, send it again.

Harry