I downloaded data from GRANIT.unh.edu, and located a geodetic survey marker nearby to our camp in Acworth, NH. Visually on the map, it is located just south of the intersection of North Shore Road and route 10 (Second New Hampshire Turnpike), in the town of Unity, New Hampshire. According to the obtained data, it is located at 43 degrees 16 minutes 50 seconds, and 72 degrees 14 minutes 39 seconds. I drove to the approximate location, parked on the side of the road, and started searching around, on the southwestern corner of that intersection- eventually I found the marker, placed in a large boulder that is also serving as an anchor point for a nearby power pole.
I turned on all 11 Nexus devices, turned on a Garmin Etrex GPS, started up Motion GPX on my smartphone... and got out my notebook and pen. A light drizzle-shower interrupted me briefly, when I ran for a towel in the car... and eventually all the devices settled down, and I was able to jot down readings from all devices. I set all to report degrees/minutes/seconds, as that was how my data reported the survey marker.
The latitude decimal degree column and the longitude decimal degree column are calculated, from the device-reported degrees,minutes,seconds data. Also, it should be pointed out that the latitude readings are N, and the longitude are W. To be used in an GIS map, the decimal degree longitude numbers would be multiplied by -1 (negative 1). The unit reported accuracy on all Nexus devices was 3, which is 3 yards radius. The reported accuracy of the Garmin Etrex is 10 feet radius. I don't have a reported accuracy for the iphone Motion GPX app. Note the only discrepancy is the survey marker!!! I wonder if I should get in touch with the USGS. On the other hand... these hand-held devices are set to WGS 1984 datum. The marker states it was reset in 1966. I wonder... if that could explain the discrepancy of just-more-than 2 full seconds of longitude.
I think... I will revisit the site, and set waypoints there, to check if the stored data (stored waypoints) is kept in decimal degrees, as the Garmin Etrex does. (Even though the Garmin Etrex is set to read-out degrees/minutes/seconds, it stores the data as decimal degree.) And then I will re-set the Nexus devices to read-out decimal degrees, and re-write those read-outs, to compare the accuracy compared to the set above. And I need to check how to access the internally stored waypoints (and tracks). Pulled off with a cable? E-mailed out to... someone? Vulcan mind-meld? Magic? More later.
We just completed the 3rd of our 7 Summer Institutes related to GIS- and I had a chance to try out a couple of the Nexus devices, using an Editable Feature Service (EFS) in ArcGIS Collector. It was raining off-and-on throughout the day, but we grabbed 30 minutes in the middle of the afternoon to go outside and collect GIS referenced data- specifically, oil spots on parking spots in the Hopkinton Middle High School (HMHS) parking lot.
We were successful in logging onto the devices, successful in downloading a basemap of the EFS using the school wifi connections... we were not as successful in collecting the data. Because the oil spots were obscured on the rain-wet asphalt, the 3 of us using the Nexus devices had to more-or-less make up pretend data as we walked along the parking lot.
In addition, the device that I was carrying did NOT have accurate GPS readings, regularly reporting poor GPS reception, and never getting accuracy better than "somewhere in a 66-foot radius". It may have been the drizzle, it may have been the saturated clouds, but Nexus device #1 was never accurate. And both Nexus device 8 and Nexus device 3 (I have numbered them for identification) seemed to get more accurate GPS readings... they both suffered from other connectivity issues. Specifically, both of those devices continuously connected to the building WIFI, or TRIED to connect to the building WIFI, causing the mapping/gathering of data to stop functioning while the WIFI attempted to connect. So some data collection was lost.
Still... we collected data with I-pads, a few smart phones and... 3 Google Nexus 7 devices- here is a map Marcel Duhaime (math teacher from Bow High School) made with that shared EFS data...
View larger map
Walking around the rain-slick parking lot with these Nexus devices, these slippery, thin, hard-to-hold devices...shielding them from drizzle... comparing them to the expensively-rubber-clad-in-waterproof-cases UNH Cooperative Extension I-pads that others were carrying... made me realize we really need to consider adding some protection to these Nexus devices. I plan on researching to find something within our budget constraints.
Also, I intend to test all 11 devices for accuracy over the coming weekend, when it will be sunny, clear and dry. I packed them all up in a newly acquired hard-shell small suitcase (that will soon be outfitted with foam lining), and will report back on the GPS accuracy testing. With regards to the connect/disconnect to WIFI issue, we decided it can be solved by simply turning off WIFI when "out of the building". An elegant solution! So, some more testing, some more research and some more tweaking is planned for the weekend.
I have located 11 neoprene sleeves to contain the devices, and am considering some scheme to acquire an appropriate sturdy shock-resistant shipping case, so that we could re-allocate some of those funds to purchase better “in the field” cases to protect the individual devices from accidental knocks and bangs and bruises and drops. It seems to me, the real risk to these devices is NOT during storage and/or transit/shipping.. .but rather, during actual individual use in the field. THAT”S where we should concentrate our efforts for protection. More about that later.
Again… the Concord store had none in stock… the near-to-my-camp Claremont store had none in stock. I emailed to Walmart.com to ask procedure, the auto-reply told me to “return the device” to the store, and re-order through online. So… I made plans to return the device, and re-ordered the replacement before actually returning (to save a trip) and … again… the ordered on-line device was “ready for delivery” within minutes of ordering. Clearly, there is a distinction with the stores, and they don't talk to each other. “out of stock on the shelf” doesn’t really mean “out of stock in the building” I drove to Claremont NH, returned the mostly-dead Google Nexus. ( All right, so maybe the device is only mostly dead… still, it would take a miracle to bring it back. I returned it).After the successful return, I visited the Walmart.com area at the back of the store, and picked up my ordered-on-line 11th Google Nexus 7 device. (We opened the box there, and turned it on. It worked. Excellent!)
Of the 11 devices, 1 totally refused to power-up / turn-on. I tried reading online about similar situations involving the Google Nexus, and found that MOST users with dead devices are able to “jump start” the battery with a short charging… followed by unplugging… counting to 15, plugging back in… and turning on the device. This trick didn’t work. I found another story of charging for 1 hour, and then doing the same… that didn’t work either. I found another story whereby the owner dis-assembled the sealed Nexus, and disconnected the battery briefly... and this supposedly revived the device. (“Whoo-hoo-hoo, look who knows so much. It just so happens that your friend here is only MOSTLY dead. There's a big difference between mostly dead and all dead. Mostly dead is slightly alive.” ) I decided AGAINST that idea, and … decided to return that 11th device.
