If you look at the output of a html5 geolocation request,
it has 14 LAT decimals.
https://www.w3schools.com/Html/tryit.asp?filename=tryhtml5_geolocation
I only find descriptions online, that 9 decimals are already
0,11mm exact.
Why are there 14 decimals?
I can hardly believe, that GPS can tell you micrometer exact position.
And also, what for would that be good?
Why? 1) to pursue precision. 2) to enable people interessed in many details, for their systems to work properly, to use them. 3) because it's very easy for developers like us, to ripoff the unnecessary (from our point of view) decimal parts.
Related
I have a number of XY coordinates and am looking to discern which country each of these are in, who knows a good service/way of doing this?
I am working with MySQL & PHP, not that its really relevant, I am o fey with consuming web services/pages and assume there must be a web-service/page somewhere which will do this, if someone can point me in the right direction that would be awesome.
How do I take: 306458,383136 and turn it into: United Kingdom (for example.)
Appreciate your responses in advance.
What you're looking for is called reverse geocoding, and e.g. Google Maps has this functionality: http://code.google.com/apis/maps/documentation/geocoding/#ReverseGeocoding
It works from a Lat/Lon coordinate, and could return even a more precise information than only a country; note that this is only an estimate - in some places, country boundaries are somewhat tangled.
If you're looking to do this offline, or if Google's/Bing's/whoever's licensing is too strict for you (e.g. you need to do a gazillion of requests per day, or need to present the result in an unorthodox format), it's possible to run your own instance of Nominatim, feed it a data extract from OpenStreetMap (under ODbL, a much more permissive license), and query that.
For example, there's a set of boundaries available at https://wambachers-osm.website/boundaries/ - just the national boundaries, so you wouldn't need to download the entire planet map.
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.
This may sound weird, but i need to know what the maximum amount of digits in a coordinate in the Google maps API is.
Say for an example, i use their "Web Services" API to find an address, then what is the longest possible lat/lng number? like xxx.xxxxx...
I see them referring to a 10 digit number (not counting the dot) in their documentation for the web services api, but i don't know if that's the max?..
Personally i haven't seen anything more than 7 digits after the dot returned, but i know google can at least search for a seemingly endless coordinate.
If anyone knows for sure what the longest coordinate you can expect returned is, please let me know.
SQL-wise:
Latitude/Longitude should use FLOAT/DOUBLE precision.
It's definitely not recommend to use e.g. VARCHAR(20) because numeric comparisons would fail for sure.
API-wise:
Same applies for the Maps JS API;
about the various Data-APIs I'm not sure (and have no time to test that)
(probably just precision-reduction/proximity...)
PHP Manual - Floating point numbers:
The size of a float is platform-dependent, although a maximum of ~1.8e308 with a precision of roughly 14 decimal digits is a common value (the 64 bit IEEE format).
update just being down-voted (5 years later) without a reason (most likely by someone, who failed to comprehend)... while newer versions of mySQL even feature a Point datatype, in order to represent coordinates... still API wise, the data is always posted as String.
I'm working on a transportation model, and am about to do a travel time matrix between 5,000 points. Is there a free, semi-reliable way to calculate the travel times between all my nodes?
I think google maps has a limit on the number of queries / hits I can achieve.
EDIT
I'd like to use an api such as google maps or similar ones as they include data such as road directions, number of lanes, posted speed, type of road, etc ...
EDIT 2
Please be advised that openstreet map data is incomplete and not available for all jurisdictions outside the US
Google Directions API restricts you to 2500 calls per day. Additionally, terms of service stipulate that you must only use the service "in conjunction with displaying the results on a Google map".
You may be interested in OpenTripPlanner, an in-development project which can do multi-modal routing, and Graphserver on which OpenTripPlanner is built.
One approach would be to use OpenStreetMap data with Graphserver to generate Shortest Path Trees from each node.
As that's 12,502,500 total connections, I'm pretty sure you'll hit some sort of limit if you attempt to use Google maps for all of them. How accurate of results do you need/how far are you travelling?
I might try to generate a crude map with travel speeds on it (e.g. mark off interstates as fast, yadda yadda) then use some software to calculate how long it would take from point to point. One could visualize it as an electromagnetic fields problem, where you're trying to calculate the resistance from point to point over a plane with varying resistance (interstates are wires, lakes are open circuits...).
If you really need all these routes accurately calculated and stored in your database, it sounds like (and I would believe) that you are going to have to spend the money to obtain this. As you can imagine, this is expensive to develop and there should be renumeration.
I would, however, probe a bit about your problem:
Do you really need all 5000! distances in a database? What if you asked google for them as you needed them, and then cached them (if allowed). I've had web applications like this that because of the slow traffic ramp-up pattern, I was able to leverage free services early on to vet the idea.
Do you really need all 5000 points? Or could you pick the top 100 and have a more tractable problem?
Perhaps there is some hybrid where you store distances between big cities and do more estimates for shorter distances.
Again, I really don't know what your problem is, but maybe thinking a bit outside the box will help you find an easier solution.
You might have to go for some heuristics here. Maybe you can estimate travel time based on a few factors like geometric distance and some features about the start and end points (urban vs rural areas, country, ...). You could get a few distances, try to fit your parameters on a subset of them and see how well you're able to predict the other ones. My prediction would be, for example, that travel times approach linear dependence from distance as distance grows larger, in many cases.
I know it's messy, but hey you're trying to estimate 12.5mio datapoints (or whatever the amount :)
You might also be able to incrementally add knowledge from already-retrieved "real" travel times by finding close points to the ones you're looking for:
get closest points StartApprox, EndApprox to starting and end position such that you have a travel time between StartApprox and EndApprox
compute distances StartError, EndError between start and StartApprox, end and EndApprox
if StartError+EndError>Distance(StartApprox, EndApprox) * 0.10 (or whatever your threshold) -> compute distance via API (and store it), else use known travel time plus overhead time based on StartError+EndError
(if you have 100 addresses in NY and 100 in SF, all the values are going to be more or less the same (ie the difference between them is probably lower than the uncertainty involved in these predictions) and such an approach would keep you from issuing 10000 queries where 1 would do)
Many GIS software packages have routing algorithms, if you have the data... Transportation data can be fairly spendy.
There are some other choices of sources for planning routes. Is this something to be done repeatedly, or a one-time process? Can this be broken up into smaller sub-sets of points? Perhaps you can use multiple routing sources and break up the data points into segments small enough for each routing engine.
Here are some other choices from quick Google search:
Wikipedia
Route66
Truck Miles
If I had lat/long data for all our leads in Salesforce, is there a way to write a query to group them, or say list all the leads within 10 miles of San Francisco, CA ?
[EDIT: Clarification]
I have thousands of leads with both a full address, and long/lats.
I want to build a query on these leads that will give me all of the leads near San Francisco, CA. This means doing GIS type work within salesforce.
I could of course filter specifically on city, or zipcodes or area code, but this presents some problems when trying to rollup a whole metro area.
Yes. You need to Reverse GeoCode them with a tool/service. In the past I have used Maporamas service but it was quite expensive and that was before Google maps and virtual earth existed so I am sure there is something cheaper(free) out there now.... Googling around I have found this and this
EDIT:
OK from What I understand you are trying to calculate the distance between 2 lat/long points. I would start by discounting the ones that where outside you sphere of (lets say) 10 miles. So from your central point you will want to get the the coordinates 10 miles, East, West, South and North. To do this you need to use the Great-circle distance formula.
From that point you have you Sales Force Data if you wish to break this data up further then you need to order the points by distance from the central point. To do this you need to use the Haversine formula
I am not sure what you language preference is so I just included some examples from SQL(mainly) and C#
Haversine Formula in C# and in SQL
Determine the distance between ZIP codes using C#
Great Circle SQL
Great Circle 2
Use GeoHash.org (either as a web service or implement the algorithm). It hashes your lat-long coords into a form that appears similar for nearby places. For example A may have a hash like "akusDf3af" and B might have a hash like "akusDf3b2" if they are nearby. Then do a SOQL query that looks for places starting with the same n characters as a known location. Your n will determine the radius of the lookup.
These are some great technical solutions that can provide very exact answers, but two things to consider:
geospatial proximity does not map neatly to responsibility
Ownership calculation seems to be done best through postal code lookups or other rules that don't allow for gaps or overlaps. Otherwise, you'll have two (or more) salespeople fighting over leads that are close to both of them, and ignore those leads that are far away from both of them.
So, if you're using geo-calculations like those above to assign ownership, just acknowledge the system will leak and create business rules to accomodate for that. But a simple postal lookup to define territories (as salesforce's own territory management feature does) might be better.
I'd suggest the problem we're trying to solve geospatially is not who owns which lead. Rather, given all the leads you own, which are nearby?
maps often offer more data per pixel than columnar reports
Again, geospatial data in a report may not be the best answer. A lead 50km away, but along a major road, is more interesting than another lead 50km away on the other side of a mountain or lake. Or a lead close to other leads is more interesting than a lead by itself.
A report can't show this, but a map can.
Salesforce has some great examples of Google Maps integrations. Instead of a columnar report called "My Nearby Leads", why not a visualforce page, with a google map inside? You're giving the user far more information than a columnar report could. They might like it better, and it's easier to implement than trying to calculate some of the equations above.
Just another perspective that may (or may not) be appropriate to the problem at hand.
This post is really old, but is showing up at the top of Google results, so I figured I would post some info to it anyways.
2 nice mapping tools are batchgeo.com and geocod.io. Geocod.io can even give you lat and long coordinates from an address.
If you just need a one time calculation, you can use Excel. Export all your leads with the lat and long. Then go to Google Maps and get the lat and long in decimal degrees for the city center of wherever you want to measure to.
Then use this formula in excel to calculate the distance between the coordinates in miles. Lat1dd and Long1dd are the coordinates for one point, and the lat2dd and long2dd are coordinate points for the other point.
=3963*ACOS(COS(RADIANS(90-lat1dd))*COS(RADIANS(90-lat2dd))+SIN(RADIANS(90-lat1dd))*SIN(RADIANS(90-lat2dd))*COS(RADIANS(long1dd-long2dd)))
After you run it, just sort the results from smallest to largest to get those results that are the closest.
I haven't done this next part yet, but conceptually it should work. We have a field that lists the major market each account is in. Example, Chicago IL. I am going to build a trigger or formula field that essentially says IF(Market="Chicago IL") then use X and Y for the lat and long. These will be hardcoded as the city center for that specific market. The query will then run each individual account's lat and long against the one from the city center to calculate a distance.
If you wanted to break the market into different zones, you could adjust your formula so it uses < and > on the lat and long fields. Everything less than X but greater than Y goes in Zone A, etc.
Hope this helps someone.