Just a quick question I have built the following code:
http://letterpool.testmode.co.uk/map.html
However with some users I am getting reports that people are getting around a 200-300 meter of their actual location.
Does any one know why ?
The W3C Geolocation API, which you're using to locate users on the test map, is intentionally agnostic to the method the browser uses to locate the device. This is a useful convenience since devices vary widely on how they locate (GPS, WiFi triangulation, cell tower triangulation, IP geolocation, manual entry, etc.) and your website probably doesn't want to deal with all of those details.
However, if you're not happy with the accuracy, there are a few options you can take advantage of that may help. The enableHighAccuracy option will hint to the device that it should prefer to use up a little more power in order to get a more precise location. You're currently using the latitude and longitude of the return value, but the API also returns an accuracy value, so you can see whether the position you're receiving is precise or not. You could also use watchPosition which will continually update the location and may eventually get a precise enough fix for your purposes (most mobile devices tend to start with low accuracy and get more refined over a few seconds or minutes).
Because geo-location is not accurate and never has been. They are probably getting the location of the closest junction box.
With me, it found the data center where my ISP operates from - miles away.
See this article.
Geolocation of course depends on the available position measurement methods. If the browser only has the IP address then it will be very inaccurate, but if it has access to a a GPS device like in a smartphone it will be pretty good.
Related
I have very important question for me. I would like to use Autodesk Reality Capture API in my app. I read the documentation to API but I did not find it. I know the position of camera and i would like to send this information to Reality Capture API. For example circle was divided in 24 parts. So I know that each photo was made every 15 degrees. Is there any parameter which gives me possibility to provide the position of camera?
There is no way of passing this kind of information to Reality Capture API (at least no official way) and even if it is debatable, there is not much use for such input.
Roughly speaking, the engine will “stitch” the given images based on common pixels/regions/patches. For complex objects, each 15 degrees might not be enough to capture the complex geometry and you will have to add more photos aiming that specific region.
The main benefit is that you can process your images, get the result, see the missing or low detail spots, take a bunch of photos of those specific spots and add them to the project, process your project again and repeat till you get a satisfying result. From this perspective, the "rule" of photos taken each 15 degrees will break very fast.
If you are getting wrong results, 80% of the time (again the Pareto principle) this is caused by missing the scenetype parameter, which defaults to aerial, when usually people expects to use the object type.
Check The Hitchhiker's Guide to ... Reality Capture API for more details.
Well I have a problem with Geolocation, when the page is initialized I have “right” location, after I refresh the page there are different location, maybe 10 meters from first. After one more refresh I have a third location, etc.. I tested on this link https://developers.google.com/maps/documentation/javascript/examples/map-geolocation , and again I don’t have a right position.
Accuracy of geolocation depends on how does your geolocation is determined. It may change.
There are a variety of ways that your
device and the location service provider
calculate your position, and some are more
accurate than others. GPS is often the most
accurate.
You may like to know
How the Geolocation API determines your location -
IP Address
Location information based
on your IP address uses an
external database to map
the IP address to a physical
location. The advantage of this
approach is that it can work
anywhere; however, often
IP addresses are resolved to
locations such as your ISP’s
local office. Think of this
method as being reliable
to the city or sometimes
neighborhood level.
GPS
Global Positioning System,
supported by many newer mobile
devices, provides extremely
accurate location information based
on satellites. Location data may
include altitude, speed and heading
information. To use it, though, your
device has to be able to see the sky,
and it can take a long time to get a
location. GPS can also be hard on
your batteries.
Cell Phone
Cell phone triangulation
figures out your location
based on your distance from
one or more cell phone towers
(obviously the more towers, the
more accurate your location
will be). This method can be
fairly accurate and works indoors
(unlike GPS); it also can be much
quicker than GPS. Then again, if
you’re in the middle of nowhere
with only one cell tower, your
accuracy is going to suffer.
WiFi
WiFi positioning uses one or more
WiFi access points to triangulate
your location. This method
can be very accurate, works
indoors and is fast. Obviously
it requires you are somewhat
stationary (perhaps drinking a
venti iced tea at a coffee house).
Is there a way to catch which method is currently being used by the device when geolocation (watchPosition) is called? i.e. if the position comes from GPS data or some sort of trangulating or ip.. Can't seem to find anything in the position object in the callback..
as far as I know, you can't get the source. The information provided came in my experimentation nowhere close to my location (it thought I was 100km away).
What you do get, is information how accurate the lat/long is. Combine that with altitudeAccuracy outlined in the specification and you can assume which service (GPS, WLAN, etc.) gave you that information.
Further, you would then use something like the Open Geo DB to nail-down in which city the user is.
My client wants some of the functionality of Google maps namely:
- geocoding
- generating maps with points based on postal code or long.lat
- optimal trip mapping
Their issues with Google maps
- cannot control outages
- postal codes are sometimes inaccurate or not updated frequently for Canada/UK
- they have no way to correct inaccurate information
They would prefer to host the mapping application themselves, but will require postal code updates.
Can anyone suggest such a product?
thanks
"cannot control outages - postal codes are sometimes inaccurate or not updated frequently for Canada/UK - they have no way to correct inaccurate information"
Outages
hosting your own mapping is the only way to control this, but you would be very very hard pushed to beat Google Maps / Bing Maps uptime over the last 5 years. Take a look at the following:
OpenStreetMap for the road imagery data, this is open source data very good in the UK (Im not sure about canada) and you can make your own changes and submit them (or just change the data you have downloaded)
Geoserver, Mapnik or MapServer will read openstreetmapdata and create the image tiles needed to create your own maps in whatever style you wish. Depending on if you dont want all countries and all zoom levels these products can create all the tiles you will need in advance, but usually they have to be created in real time and cached. You need a BIG fast server to manage tile crunching
Openlayers or Leaflet are open source javascript mapping platforms that will display your tiles for you
Obviously this is just for road maps, aerial imagery would cost you an absolute fortune.
Post Code Data
Many people do not realize that UK postcode data for latitude and longitude is now completely free and available to download every quarter from the official source (ordinance survey) http://www.ordnancesurvey.co.uk/oswebsite/products/code-point-open/index.html.
This is the same data source Google will use and there is none better but it will always contain inaccuracies and always be a few months out of date.
Finally
Hopefully that answer the question you asked and gives you information to inform your client. Now for the question you didn't ask "Is this approach good value to my client?".
I won't presume to know your business or client, however what I described above is possible but with one to many months of work involved to get it all working together and even then it wont have any where near the performance or uptime of something like google /bing maps and only offers a small subset of their features.
I think you're looking for something like Caliper-It's a very custom, and I would expect expensive, solution. Not suggested.
http://www.caliper.com/GISMappingSoftwareDevelopment.htm
One solution could be to use two different mapping services and compare their results, this way there's a much better chance the data is accurate. You can also fix inaccurate data by creating a system which acts as a barrier between the API and your user, where data you know is inaccurate is corrected before it's displayed. Not sure exactly what you're doing though, so this might not work for you.
Is trip mapping/routing the basic functionality you want to do?
Before rushing into rolling your own, I'd suggest a good think about the consequences of doing so. The first that springs to mind is whilst the pros are that you can now control your data, the cons are that you now control your data.
So you are going to have to consider where and when you get updates and the processes you are going to have to employ to keep your maps in sync with the rest of the world. There are a lot of headaches involved in these things which is why so many people use externally hosted solutions such as Googles.
A friend of mine brought up this questiont he other day, he's recently bought a garmin heart rate moniter device which keeps track of his heart rate and allows him to upload his heart rate stats for a day to his computer.
The only problem is there are no linux drivers for the garmin USB device, he's managed to interpret some of the data, such as the model number and his user details and has identified that there are some binary datatables essentially which we assume represent a series of recordings of his heart rate and the time the recording was taken.
Where does one start when reverse engineering data when you know nothing about the structure?
I had the same problem and initially found this project at Google Code that aims to complete a cross-platform version of tools for the Garmin devices ... see: http://code.google.com/p/garmintools/. There's a link on the front page of that project to the protocols you need, which Garmin was thoughtful enough to release publically.
And here's a direct link to the Garmin I/O specification: http://www.garmin.com/support/pdf/IOSDK.zip
I'd start looking at the data in a hexadecimal editor, hopefully a good one which knows the most common encodings (ASCII, Unicode, etc.) and then try to make sense of it out of the data you know it has stored.
As another poster mentioned, reverse engineering can be hairy, not in practice but in legality.
That being said, you may be able to find everything related to your root question at hand by checking out this project and its' code...and they do handle the runner's heart rate/GPS combo data as well
http://www.gpsbabel.org/
I'd suggest you start with checking the legality of reverse engineering in your country of origin. Most countries have very strict laws about what is allowed and what isn't regarding reverse engineering devices and code.
I would start by seeing what data is being sent by the device, then consider how such data could be represented and packed.
I would first capture many samples, and see if any pattern presents itself, since heart beat is something which is regular and that would suggest it is measurement related to the heart itself. I would also look for bit fields which are monotonically increasing, as that would suggest some sort of time stamp.
Having formed a hypothesis for what is where, I would write a program to test it and graph the results and see if it makes sense. If it does but not quite, then closer inspection would probably reveal you need some scaling factors here or there. It is also entirely possible I need to process the data first before it looks anything like what their program is showing, i.e. might need to integrate the data points. If I get garbage, then it is back to the drawing board :-)
I would also check the manufacturer's website, or maybe run strings on their binaries. Finding someone who works in the field of biomedical engineering would also be on my list, as they would probably know what protocols are typically used, if any. I would also look for these protocols and see if any could be applied to the data I am seeing.
I'd start by creating a hex dump of the data. Figure it's probably blocked in some power-of-two-sized chunks. Start looking for repeating patterns. Think about what kind of data they're probably sending. Either they're recording each heart beat individually, or they're recording whatever the sensor is sending at fixed intervals. If it's individual beats, then there's going to be a time delta (since the last beat), a duration, and a max or avg strength of some sort. If it's fixed intervals, then it'll probably be a simple vector of readings. There'll probably be a preamble of some sort, with a start timestamp and the sampling rate. You can try decoding the timestamp yourself, or you might try simply feeding it to ctime() and see if they're using standard absolute time format.
Keep in mind that lots of cheap A/D converters only produce 12-bit outputs, so your readings are unlikely to be larger than 16 bits (and the high-order 4 bits may be used for flags). I'd recommend resetting the device so that it's "blank", dumping and storing the contents, then take a set of readings, record the results (whatever the device normally reports), then dump the contents again and try to correlate the recorded results with whatever data appeared after the "blank" dump.
Unsure if this is what you're looking for but Garmin has created an API that runs with your browser. It seems OSX is supported, as well as Windows browsers... I would try it from Google Chromium to see if it can be used instead of this reverse engineering...
http://developer.garmin.com/web-device/garmin-communicator-plugin/
API Features
Auto-detection of devices connected to a computer Access to device
product information like product name and software version Read
tracks, routes and waypoints from supported recreational, fitness and
navigation devices Write tracks, routes and waypoints to supported
recreational, fitness and navigation devices Read fitness data from
supported fitness devices Geo-code address and save to a device as a
waypoint or favorite Read and write Garmin XML files (GPX and TCX) as
well as binary files. Support for most Garmin devices (USB, USB
mass-storage, most serial devices) Support for Internet Explorer,
Firefox and Chrome on Microsoft Windows. Support for Safari, Firefox
and Chrome on Mac OS X.
Can you synthesize a heart beat using something like a computer speaker? (I have no idea how such devices actually work). Watch how the binary results change based on different inputs.
Ripping apart the device and checking out what's inside would probably help too.