[HOT] Feedback about smartphones use for OSM field surveys
borisC at osm-at.org
Wed Jun 13 12:22:03 BST 2012
No comments on 'garmin vs. logger', I second every word.
> ... SIRF III, despite your warning... would be interested to read
> why you warn against it?
Sirf3 was designed years ago, and is technically somewhat outdated.
Recent chipsets offer a significantly better input gain which leads to
better results, esp. in bad conditions. Also the algorithms to filter
signal reflections from buildings (the main reason for low accuracy in
towns) have improved the past years.
But the most important thing is: sirf3 was designed with car
navigation in mind.
In its factory configuration it is definitely unsuited for other
tasks like logging while walking or cycling. It tries to smoothen the
track and eliminates all moves a car wouldn't do, like sharp turns.
It even stops recording until you have reached a speed of 5 km/h or
travelled a distance of approx. 20m.
These features can be turned off, but the software to do so is hard to
get, undocumented and there is actually a chance to brick your device.
Also there are far too many parameters to set, so a non-pro will never
be able to fine tune his device.
I have been using a sirf3 powered TomTom receiver before I bought the
WBT202, and was stunned that it got completely confused sometimes (it
usually needed 2 minutes to catch up from a sudden u-turn).
Doubtlessly Garmin has tuned the chip to be useful for their devices,
however you cannot expect the same from every manufacturer.
I don't know the setup program for MTK chips, but the one for UBlox is
really user friendly, it offers presets for all use cases. Also the
modern chips are far more flexible in every preset, so fine tuning is
not that important any longer.
Today (Wednesday, June 13, 2012) at 09:07 you dropped the lines:
> I would be interested to know how you would rate external data
> loggers against "classical" Garmin eTrex or similar devices?
> On the + side of the eTrex-like I see:
> ° More robust and usually better chip than smartphones (but
> probably similar to data loggers' chips)
> ° GPS chip and map on the same device (unlike data loggers)
> ° Relatively good battery life (with my eTrex 20 I can easily
> record for a full day. And if I'm somewhere without power outlets, I just take a few extra batteries)
> ° OSM (or other) data can be displayed as background, which
> makes it much easier to see "live" what has already been mapped,
> what hasn't, and what can be corrected
> ° Coupling GPS and GLONASS can significantly improve the reception in some areas
> On the - side:
> ° Real pain in the ass when it comes to log polygons (= closed ways)
> ° Real pain in the ass (2) to type in waypoints names (a
> sheet of paper is always better for that)
> On the + side of the data loggers:
> ° Extremely compact
> ° Best battery life
> ° Cheap
> But on the - side:
> ° Needs a second device to visualize tracks and background data
> ° If paired with another device through bluetooth, this will
> vastly reduce the batterylife (at least for the 2nd device)
> Now, have you seen significant difference in positional accuracy
> between such data logger and eTrex-like devices? I am so far very
> happy with my eTrex20 (and thus with SIRF III, despite your
> warning... would be interested to read why you warn against it?)
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