Anyone reverse Geocoded - say lang/lat delivers Address

[peteconway]

Hi everyone, just wondering - have a need to determine the address or location from the longitude latitude or the geocode done it in a dialog that would help me out? Just thought i'd ask before heading down the discovery path. Best regards to all for the coming holiday season just a month away.

[christappan]

Re: Anyone reverse Geocoded - say lang/lat delivers Address

Pete, you may have figured this out already and I know addresses likely read differently in Austrailia than the US, but I put this together for my own use this afternoon and thought I'd share.

FUNCTION geoAddrFromLatLon AS P (lat AS C, lon AS C )

string = "http://maps.googleapis.com/maps/api/geocode/json?latlng=" + lat + "," + lon + "&sensor=false"

jsonReq = http_get(string)

jsonBody = json_parse(jsonReq.body)
fullAddress = jsonBody.results.[1].formatted_address

dim addr as P
addr.Street = word2(fullAddress,1,",")
addr.City = word2(fullAddress,2,",")
addr.State = substr(word2(fullAddress,3,","),2,2)

geoAddrFromLatLon = addr

END FUNCTION

[peteconway]

Re: Anyone reverse Geocoded - say lang/lat delivers Address

Thanks for thinking of me Chris, I got stuck on a few other issues and this one slipped a bit - was just going to re visit it. Good timing - will give it a go and come back to you. Best wishes for the coming holiday season mate.

[chadbrown]

Re: Anyone reverse Geocoded - say lang/lat delivers Address

This works fantastic!!

[Lance Gurd]

Re: Anyone reverse Geocoded - say lang/lat delivers Address

Thanks very much, will be adapting for the UK

[christappan]

Re: Anyone reverse Geocoded - say lang/lat delivers Address

Glad you all got something from it.

Just a follow-up note that you may not get an exact address, which is probably assumed, but Google actually returns an address range sometimes (e.g. 1000-1040 Main Street), so I later made a less-than-ideal-but-safer modification to get the average address value in the range if that's the case:

FUNCTION geoAddrFromLatLon AS P (lat AS C, lon AS C )

string = "http://maps.googleapis.com/maps/api/geocode/json?latlng=" + lat + "," + lon + "&sensor=false"

jsonReq = http_get(string)

jsonBody = json_parse(jsonReq.body)
fullAddress = jsonBody.results.[1].formatted_address

dim addr as P
addr.Street = word2(fullAddress,1,",")

streetNum =word2(addr.Street,1," ")
if like("*-*",streetNum)
	street =  stritran(addr.Street,streetNum,"")
	streetNum1 = convert_type(word2(streetNum,1,"-"),"N")
	streetNum2 = convert_type(word2(streetNum,2,"-"),"N")
	streetNum = convert_type(((streetNum1 + streetNum2)/2),"C")
	addr.street = streetNum + " " + street
end if

addr.City = word2(fullAddress,2,",")
addr.State = substr(word2(fullAddress,3,","),2,2)
addr.Zip = stritran(word2(fullAddress,3,","),addr.State + " ","")


geoAddrFromLatLon = addr

END FUNCTION

Also, in terms of your design, I found that when called from a component via an ajax callback, the location functions only work if the component is on an a5w page (i.e. not called on a "virtual page" via javascript).

[peteconway]

Re: Anyone reverse Geocoded - say lang/lat delivers Address

You are a good man Chris, thanks.

[christappan]

Re: Anyone reverse Geocoded - say lang/lat delivers Address

God knows the vast majority of my application is slight variants on code and ideas I got from others on the forum, yourselves included. Thought I'd go one step further: http://screencast.com/t/2jCTfbE5P.

I lied. The button calls an Action Javascript Geolocation Functions function that fills in hidden fields with the latitude and longitude. Then an onChange Event on the latitude field calls the ajax callback that takes it from there.

[peteconway]

Re: Anyone reverse Geocoded - say lang/lat delivers Address

Good on mate - thanks - teaching and learning is what this forum is about.

[Keith Hubert]

Re: Anyone reverse Geocoded - say lang/lat delivers Address

Good on mate - thanks - teaching and learning is what this forum is about.

That's a good one Pete, how about those great videos you made, care to share?

[peteconway]

Re: Anyone reverse Geocoded - say lang/lat delivers Address

Gee mate that was a long time ago now, i'll have to think about it, I am for all to move towards Alpha Anywhere after the success I've had with it, so showing old methods may just cause problems.

[jmarciniak]

Re: Anyone reverse Geocoded - say lang/lat delivers Address

Hi, I am a total newbie, and am working on a mobile app that, when a button is pushed, I would like to get the current location from the device, then geocode that lat/long into an address as in the function given in this thread. Then, I would like to take that address info and present it to the user and have them confirm that the address is accurate before saving the lat/long to the database. Could someone please help me with this. I already have the code retrieving the current location from the device, but I am struggling to figure out how to pass that information to the xBasic function and get the result.

Thanks in advance for any help,

Jim M.

Glad you all got something from it.

Just a follow-up note that you may not get an exact address, which is probably assumed, but Google actually returns an address range sometimes (e.g. 1000-1040 Main Street), so I later made a less-than-ideal-but-safer modification to get the average address value in the range if that's the case:

FUNCTION geoAddrFromLatLon AS P (lat AS C, lon AS C )

string = "http://maps.googleapis.com/maps/api/geocode/json?latlng=" + lat + "," + lon + "&sensor=false"

jsonReq = http_get(string)

jsonBody = json_parse(jsonReq.body)
fullAddress = jsonBody.results.[1].formatted_address

dim addr as P
addr.Street = word2(fullAddress,1,",")

streetNum =word2(addr.Street,1," ")
if like("*-*",streetNum)
	street =  stritran(addr.Street,streetNum,"")
	streetNum1 = convert_type(word2(streetNum,1,"-"),"N")
	streetNum2 = convert_type(word2(streetNum,2,"-"),"N")
	streetNum = convert_type(((streetNum1 + streetNum2)/2),"C")
	addr.street = streetNum + " " + street
end if

addr.City = word2(fullAddress,2,",")
addr.State = substr(word2(fullAddress,3,","),2,2)
addr.Zip = stritran(word2(fullAddress,3,","),addr.State + " ","")


geoAddrFromLatLon = addr

END FUNCTION

Also, in terms of your design, I found that when called from a component via an ajax callback, the location functions only work if the component is on an a5w page (i.e. not called on a "virtual page" via javascript).

[Steve Workings]

Re: Anyone reverse Geocoded - say lang/lat delivers Address

I just delivered exactly this to a customer Jim. This is some of the Xbasic in my AJAX Callback - see if it helps:

	' Use Google API for reverse geolocation:
	'https://developers.google.com/maps/documentation/geocoding/
	' See section on "Reverse Geocoding"
	dim p as P
	url = "http://maps.googleapis.com/maps/api/geocode/xml?latlng=" + vlat + "," + vlon + "&sensor=false"
	p = http_get(url)
	result = p.body
	beginstr = "<formatted_address>"
	endstr = "</formatted_address>"
	paddress = extract_string(result, beginstr, endstr)
	paddress = stritran(paddress, ", USA")
	e._set.device_street_address.value = paddress

[christappan]

Re: Anyone reverse Geocoded - say lang/lat delivers Address

Not sure how you're populating the latitude and longitude in your component, but I hid those fields. Then, in their onChange event, I created an Ajax Callback taht simply called a function called getAddrFromCurrLoc.

In the XBasic functions, I have this:

function getAddrFromCurrLoc as c (e as p)

lat = e.dataSubmitted.Latitude
long = e.dataSubmitted.Longitude

if lat <> "" .and. long <> ""
	address = geoAddrFromLatLon(lat,long)

	e._set.mi_street.value = address.street
	e._set.mi_city.value = address.city
	e._set.mi_state.value = address.state
	e._set.mi_zip.value = address.zip

	getAddrFromCurrLoc = "{dialog.Object}.setValue('LATITUDE','');{dialog.Object}.setValue('LONGITUDE','');"
else
	getAddrFromCurrLoc = ""
end if

So when the value changes in the latitude or longitude field, this ajax callback runs and fills in the mi_street field, mi_city field, mi_state field, mi_zip fields in the component. This was written for a Dialog component but the grid would be very similar.

Steve,
I wanted to point out that you're doing almost the same thing I did in my code and may be handling errors differently, but you might want to note how I chose to handle Google returning inexact addresses.

[jmarciniak]

Re: Anyone reverse Geocoded - say lang/lat delivers Address

First, I would like to thank christappan and Steve Workings for your replies. These both helped a ton.

Now that I have my test component (attached here MySampleComponent.a5wcmp) retrieving the current location (automatically via the Action JavaScript "Ajax Callback Action"), I have a new question:

Q: When I run this component, and allow location services to work, I get the lat/long returned into the text boxes on the UX, but the other named elements (defined via HTML in the static text definitions) do not get updated to the address values. Can someone explain why? The code I have was derived from a video I watched, as well as from the prototype code itself. I am very confused.

Another odd behavior:

In my Xbasic function, I have the following statement:

if e.__locationFound = .t.

When I execute this code in my browser, it ALWAYS falls through to the "else" statement, regardless of whether or not I allow the location to be given. If I remove the " = .t." from the statement, then the component works as expected when I allow the location to be given, but throws an error "e.__locationLatitude subelement not found" when I deny location services. Now I am REALLY confused.

Thanks in advance!!!

P.S. Although I am very new to Alpha, I am already really impressed with what it can do, and how easy it is.