Tue., Nov. 29th

We went up on the roof above the lab window to see if we could get more accurate GPS coordinates there, using the MotionX-GPS app.

My iPhone says:

• Lat.:   30* 25' 42" (N)
• Lon.:  84* 17' 06" (W)
• Alt.:    97'
• Acc.:  56'

On Google Maps, this looks to be on the centerline of our wing of the building, about 30' away from the edge where our windowsill is.

Ray's iPhone says:

• Lat.:    30.428250
• Lon.:   84.284997
• Alt.:    131'
• Acc.:   56'

On Google Maps, this looks to be almost exactly in the right place.

Unfortunately, the iPhone is unable to acquire a fix at all in the window, so we are unable to compare it with the DeLorme to try to figure out whether the position discrepancy is due to the location or to something about the DeLorme.  But at least we've ruled out the problem being an inaccuracy in Google Maps / Google Earth (since Ray's phone, at least, agrees exactly with Google, within a couple of feet, as to where our window is, and my phone agrees almost exactly, within about 30' or so).

Aha, just got a fix in the windowsill from my iPhone, it says:

• Lat.   30* 25' 40" N
• Lon.  84* 17' 07" W
• Alt.    238 ft
• Acc.  156 ft

Cool, this is also over near Ware-Rhaney, so this confirms (more or less) that it's probably the windowsill location (and not the DeLorme unit itself) that is causing the positional inaccuracy problem.

[/] Need to make sure the POSHOLD location is as accurate as possible, WRT our real location.  OK, updated that code now with the slightly more accurate coordinates 30*25.694,N,084*17.1,W (on top of our window, instead of at corner of the wing).  Rebuilt firmware, recompiling gelware in Quartus...  Also need to rebuild the EEPROM config file... (Rev_A.jic)  Done & burned it.

Pascal dropped in and showed me the blueprints he got from the architecture firm of the I-beams, sprinklers, lighting, and vents (4 separate sheets).  He is going to work this information into the next presentation.  He also said that Reid Lambdin OK'd the idea to put the detectors on shelves instead of hanging them from I-beams.

Aarmondas reminded me that we had agreed to reschedule the presentation date/time to Friday of next week.  It will have to be 4 pm since Drifters is at 3 pm.  I emailed an updated announcement to the BB group.

I asked Aarmondas also to schedule a date/time either next week, during finals week, or in the 1st two weeks of classes in January for me to present to the ECE students the current design of the Python server software, so that the students will be familiar with the capabilities of what's already there and can build upon it for the visualization etc.

I'm starting a new overnight run to see if the time accuracy seems any different than it did in my experiments last Winter/Spring.  I think our POSHOLD position reference is more accurate now (due to both improvements in aerial photography on Google Maps / Google Earth - closer to overhead view - as well as to Ray's phone, which I think is an iPhone 4, apparently having a more accurate GPS than my 3GS does).  Tomorrow I'll do a plot showing the cumulative phase wander of the GPS's PPS signal vs. the OCXO clock, and look at the frequency and magnitude of any significant excursions that happen when time lock is temporarily lost.