My goal is to display various shapes(polygons, points, linestring) on google maps by using data entered into a Postgis database dynamically(i mean by that we can see modifications in the map in real time).
I was looking for a way to do this that used the spatial structure already provided in postgis(already designating if shape is a linestring or polygon, etc) instead of parsing out the coordinates and then re-entering spatial structure in google maps. I saw that google maps api is now compatible with kml data formats. And then I read that i have to convert postgis data to kml format.
I've done some reading in the forums about the actual process of converting postgis data to kml via FWTools, but didn't see anything that would help me. I'm new to kml but am familiar with postgis and perl and PHP. Is there a tutorial for the process of converting postgis data to kml? Where can I get started? Thanks for any help
You can use PostGIS to convert to KML directly:
SELECT ST_AsKML(geometry) from MyTable;
ST_AsKML is one of several output formats, including WKT, GML, GeoJSON, etc.
To show dynamic data in Google Earth, a common pattern is to use KML with a NetworkLink element. Have the link's viewRefreshMode equal to onStop and Google Earth will make requests (to a URL served by PHP, presumably) with bounding box parameters attached. Use the bounding box to query features in the PostGIS database, and return results as kml. This is great if you have lots and lots of features, but only want to retrieve those in the region the user is looking at.
Depending on the complexity of your application, you may also want to look at GeoDjango. (Familiarity with PostGIS is a big head start!)
You can get a textual representation of the spatial data from a Postgres DB using a text conversion function, like
SELECT AsText(MyGemoetry) from MyTable
then you parse the string, create your objects using various API functions - depending on the PostGIS geometry type - and append these object to the main GE plugin object in a DOM like way.
If you are familiar with JavaScript and have a fundamental knowledge of XML, a good start is http://code.google.com/apis/earth/documentation/reference/
Don't forget to specify unique ID's to your objects so you can find them later to drop/modify.
Maybe you can get some inspirations here, display the linked "locator.js" file and look at function PaintSubField(Coord) ... this is another way, bit crude but effective, avoiding to mess around with too many individual parent/child objects and structures
You also may want to consult sample applications and use the code playground for "rapid prototyping"
re "realtime" you need at least an event that you can link your generation/redraw routines to.
Good luck
MikeD
Related
I am looking for pointers for libraries or methods that would be able to generate full text from the structured information returned by Wikidata - if possible in multiple languages.
To be clearer: from data like the one provided here (this is the JSON version) I would like to be able to generate text similar to the intro paragraph of the wikipedia page for the same item:
Orvieto Cathedral (Italian: Duomo di Orvieto; Cattedrale di Santa Maria Assunta) is a large 14th-century Roman Catholic cathedral dedicated to the Assumption of the Virgin Mary and situated in the town of Orvieto in Umbria, central Italy.
The reason is that the text is provided by Wikipedia for all those cases where a page exists, but I would like to have something also for the Wikidata items without a wikipedia page.
My problem #1 here is: I don't know what something like this is called, so I have no idea what to google for. Any pointers to start from are appreciated, including services or APIs.
This problem falls under the Data to text generation task. I do not know of any services that are currently offering solution. You can look at WEBNLG challenge which has the same objective and similar data. AFAIK mostly template based methods are used to automatically insert data from wikidata into wikipedia as text.
I have a Postgis table of about 200 entries for which I have to enter lat/lon coordinates. I use QGIS to process and display them. Is there a way of clicking at the QGIS map and thereby entering the coordinates into the Postgis table?
I can find the coordinates on the map, copy the coordinates and enter them in the table. But that is a lot of work and it is error prone. I browsed thru all plugins, found the digitizing tools promising but this does not do what I want. I googled this specific question but didn't find a clue.
Is what I want possible at all?
I am rather a noob at gis and qgis so it took me some time before I had the right keywords to search with. And the right keyword for what I want to do apparently is "digitize". What I want is partially possible. Links that helped me are:
https://www.igismap.com/digitization-in-qgis-exploring-tools-for-digitizing/
https://www.qgistutorials.com/en/docs/digitizing_basics.html
https://gis.stackexchange.com/questions/41799/adding-shapefiles-to-postgis-database
The gist of it is:
enable the advance digitizing toolbar: view > toolbars > advanced digitizing toolbar
create a new shapefile layer: layer > create new shapefile layer. Don't forget the correct fields, in my case the name of the location. Also try to remember where you store the file (it will be a shapefile), you later need that to import the shapefile into postgis
enable the edit state of the current layer, enable the type of shape you want to import. In my case they were points
click on each location, a dialog pops up with the attributes you should add
later on you should import the shapefile, you need the third link for that together with your memory of where you stored that #$#%$& file
I am building an Angular test preparation app (with Laravel 5.1 API). One of the requirements is to allow the user to print a certificate of achievement.
The client wants the person's name and credentials interpolated into the document (e.g., highlighted below). Here is a snapshot of the PDF template they sent:
The way I'm handling PDF viewing is simply by storing the file on S3 and giving them a link to that file.
Interpolating information into a PDF doc doesn't seem trivial and I haven't found much information on programmatically allowing this, but there are tools like DocHub, that allow you do edit while viewing the PDF.
I'm interested in learning:
is doing this programmatically trivial?
are there 3rd party tools I'm unaware of?
would I even be able to send this information along to the S3 link to interpolate in the first place?
Using PDF as a format for editing is usually a bad choice. If you have a form with fixed fields, then it's easy. Create a PDF template with an interactive form. In this form, based on AcroForm technology, you'll define fields with fixed coordinates, and a fixed size. You can then add content to these fields.
One major disadvantage with this approach is the lack of flexibility. Did you notice that I used the word "fixed" three times in the previous paragraph? If text doesn't fit the predefined field, you're out of luck. If the field is overdimensioned, you'll end up with plenty of white space. This approach is great if you can predict what the data will be like. A typical use case is a ticket or a voucher. For instance: the empty form is a really nice page, with only a couple of fields where an automated system can put a name, a date, a time, and a seat number.
This isn't the best approach for the example you show in your screen shot. The position of every line of text, every word, every character is known in advance. If you want to replace a short word with a long word (or vice-versa), then all those positions (of each line, of the complete page, possibly of the complete document) need to be recalculated. That's madness. Only people with very poor design skills come up with such an idea.
A better idea, is to store the template as HTML. See for instance chapter 5 of iText's pdfHTML tutorial, where we have this snippet of HTML:
<html>
<head>
<title>Invitation to SXSW 2018</title>
</head>
<body>
<u><b>Re: Invitation</b></u>
<br>
<p>Dear <name>SXSW visitor</name>,
we hope you had a great SXSW film festival experience last year.
And we would like to invite you to the next edition of SXSW Film
that takes place from March 9 until March 17, 2018.</p>
<p>Sincerely,<br>
The SXSW crew<br>
<date>August 4, 2017</date></p>
</body>
</html>
Actually, it's not really HTML, because the <name> tag and the <date> tag don't exist in HTML. All HTML processors (browsers as well as pdfHTML) ignore those tags and treat their content as if the tag was a <span>:
It doesn't make much sense to have such tags in the context of pure HTML, but it does make a lot of sense in the case of pdfHTML. With pdfHTMLL, you can configure custom tags, and have a result that looks like the PDFs shown below:
Look at the document for "John Doe" and compare it with the document for "Bruno Lowagie". The name "John Doe" is much shorter than my name, hence more words fit on that first line. The text flows nicely (we could also have chosen to justify the text on both sides). This "flow" is impossible to achieve with your approach, because you will never get a PDF template to reflow nicely.
OK, I get it, you probably say, but what about the practical aspects? You talk about a Java / .Net library, but I am working with Laravel and Angular.js. First, let me tell you that I don't think you'll find any good PDF tools for Laravel or Angular.js, because of the nature of PDF and those development environments (in my opinion, those technologies don't play well together). Regardless of my opinion, this shouldn't be much of a problem for you because you work in an Amazon environment. AWS supports Java, and the Java code needed to get pdfHTML working is minimal. Most of the code samples I wrote for the pdfHTML tutorial are shorter than 15 lines. So why not try Java and pdfHTML?
If you're already using Amazon services, why not use an amazon lambda function, in combination with iText7 (java), to generate the pdf on demand?
That way, you are guaranteed that the pdf is correct, and has nice layout every time.
Generating the pdf can either be done by:
converting HTML,
programmatically creating your entire document,
filling and flattening an XFA form.
I think for your use-case, either option 1 or 2 are the most sustainable.
I am researching the way to improve efficiency of using cache in Maya. For wide use, Alembic Cache is a good choice as I know. So, I try to use it as replacement of Geometry Cache(mcx). But Alembic Cache has a limitation of matching names of targets. On behalf of Geometry Cache, is there any aid for using Alembic Cache?
I just answered this in a previously asked question.
To overcome the non-matching name target problem:
When you import the abc file into Maya, it creates an abc Node in the Maya scene. If the object name doesn't match your scene's object name, you can connect it manually.
The way you do this is as follows.
The alembic node has a bunch of output plug Arrays, like outPolyMesh, outNSurface etc. These contain the outputs. If your render object is a mesh, you will be able to find the corresponding output plug inside the outPolyMesh array. In your connections editor, just connect the corresponding outPolyMesh[i] plug into your inMesh plug of your render model's shape node.
Hope that was useful.
Is it possible to highlight a list of countries with a different colors?
I need to display some countries' statistics on the world map.
Now I use an image and fill a region with color (calculated for each country) by country's coordinates. It's a simple solution and it works well. But now I need to specify the countries' name too (and I think it's not the last customization).
There is a polygon solution, but it uses an array of coordinates. I don't think it's a suitable solution to highlight countries's territory.
I haven't found a solution yet. Any suggestions?
Thanks in advance.
Highlighting countries or regions to support statistics is known as Choropleth Mapping
, but unfortunately there usually isn't direct library support for Choropleth maps bundled into an online map API. This means you'll have to create your own framework, but fortunately it is possible to create one - I wrote an example using jQuery + HERE Maps to
answer the question here
Updated WKT solution now available
Access to KML shapes is no longer required, since the Geocoder API now offers an IncludeShapes attribute which returns the shape of a country in WKT format. A WKT parser can be found here.
A simple WKT choropleth example can be found here.
KML Base solution
For any framework you will need to have a file holding the boundaries of the countries or regions you need. The example uses a KML file, but you could also start with polygons if you had them. Country borders are a political minefield, which is the reason I guess most online mapping APIs steer clear of them. As a hint: try starting with something like http://geocommons.com/overlays/119819 and simplify it as much as possible to speed up the rendering- many small wiggles in the coast lines and small outlying islands are unnecessary.
Of course you could also try searching for "create choropleth map" from a search engine of your choice and use an tool to create a static image for your data (potentially at several zoom levels) and then use this as the basis of an map tile overlay. This requires a lot more work up front, but would push all the calculations server side and hence be faster to display.
Working example can be found on GitHub here
You could put the country's name into the image. It's not that difficult to place text into an image. The only tricky bit is if you are using tiles, you need to deal with names that cross tile boundaries by drawing the name once for each tile.