I was using following filter encoding establishing new WFS connection in QGIS i.e.
https://sedac.ciesin.columbia.edu/geoserver/ows?version=1.1.0&typenames=gpw-v3:gpw-v3-coastlines&outputFormat=application/json&CQL_FILTER=dwithin(the_geom, POINT(37.696 14.964), 20, kilometers so as
to select lines within 20km from above point coordinate.
Though the output is displayed however,line features seems to be far from the 20 km distance from the above point. Why is this happening?
That is an old version of GeoServer which uses the units of the projection not the ones specified in the DWITHIN so you will need to use a projection that is in metres (EPSG:3035?).
Related
I am working in Arcgis 10.3.1 and I am trying to add some random points into a polygon shapefile as the center for circular sampling plots, however, every time I use the minimum allowed distance (I use 15 m because the plot radius will be 10 m) I get an error.
Without using the minimum allowed distance it works fine but usually the samples spacing is not right.
I was thinking maybe there was not space in the area to have such spacing but the area i 4000 m2 and a 10m radius circular plot is only around 300m2 (I need only 4). Even if I use 2m distance I get the error.
I am not sure if I am using it right. Is there any other way to add random points?
Any imput is welcome
Sorry I just figure out what was happening.
Apparently there was a file with the same name as my output and that is why I got the error codes.
using DJIWaypointMissionHeadingTowardPointOfInterest as heading mode in DJIWaypointMission i can automatically rotate the drone to heading vs a POI, but is there a way to also automatically tilt the camera to frame the POI?
(unlucky also the "pointOfInterest" have no altitude property)
also i think that would be better change/define the heading mode in the DJIWaypoint instead to be a property of the entire DJIWaypointMission, is it possible?
I'm adding to what Ken said.
When you use 'isGimbalPitchRotationEnabled' you can set a pitch angle in each waypoint. The drone will change the pitch angle in a linear motion between each 2 waypoints.
Of course this will not work when during a flight between the 2 points the drone gets closer to the POI and than backs away.
What I'm doing in my app is dividing the straight line between the 2 points into several straight sections and calculating the correct pitch at each point. As I divide the original line I calculate the error (the difference between the calculated pitch and the linear extrapolated pitch). If the error is greater than some value (5 degrees, for example) I divide the line recursively and re-calculate the pitch, until the error at each point is small enough. It takes some geometric calculations when preparing the mission, but it produces amazing fly-by shots.
Take a look at these settings:
isGimbalPitchRotationEnabled and gimbalPitch
This isn't a 'true' location though because the pitch divides equally based on the distance between the waypoints but it's close.
In my app I manually control the gimbal but that means a connection must be maintained or the gimbal stops moving.
Yes, it would be nice if the POI in waypoints was a true POI functionality and I've made the suggestion many times but to no avail so far. I'd like to see the POI be a per waypoint (as a LocationCoordinate 3D) rather than the current, 1 POI for the whole mission.
I'd also like to see the location in waypoint to be consistent and be of type LocationCoordinate3D.
I want to match symmetry of object contours. I tried using matchShape(), computeDistance(), Humoments() from opencv 3.0 library. But none of them is close to what I want.
Following are the images on which I am working.
Good Shape-1
Defected
I expect to get highest value of dis-symmetry for image-2(named Defected)
You can do it yourself, by using several simple tools:
Find the centroid
Use PCA (http://docs.opencv.org/master/d1/dee/tutorial_introduction_to_pca.html#gsc.tab=0) to find the main axis
Rotate the shape so that the main axis points up
In each row, count the number of pixels on either side of the center and compare (There should be a single center coordinate, probably using the median value of all rows centers)
You can tune your own thresholds to fit the problem.
I have some geojson data for Japan, which I managed to position properly on a mercator projection, but I'm a bit lost as to how to position it properly using an albers projection, other than trial and error.
Is there a good tool to use?
blocks example: http://bl.ocks.org/4043986
long, lat for japan (wikipedia):
latitudes 24° - 46°N,
longitudes 122° - 146°E.
geojson link: https://gist.github.com/raw/4043986/f53b85ab0af1585cd0461b4865ca4acd1fb79e9f/japan.json
As of now, it's the version 3 of D3.js.
It might be worth looking at the original source albers.js at github, which contains :
d3.geo.albers = function() {
return d3.geo.conicEqualArea()
.parallels([29.5, 45.5])
.rotate([98, 0])
.center([0, 38])
.scale(1000);
};
Now, d3.js use combination of projection.rotate and projection.center to place center of the projection to long 98°W, lat 38°N (around Hutchinson, Kansas).
From Geo Projections API,d3.geo.conicEqualArea()
.parallels([29.5, 45.5]) sets the Albers projection’s two standard parallels latitudes 29.5°N and
45.5°N, respectively. But what is two standard parallels?
To understand what parallels setting is, one need to know that Albers projection is a kind of conic projection.
A conic projection projects information from the spherical Earth to a cone that is either tangent to the Earth at a single parallel, or that is secant at two standard parallels.
Choosing the best standard parallels setting seems to be a subtle task, of which the goal is to minimize the projection distortion when mapping between surfaces. Anyway, choosing the two values to be closed to a country top/bottom edges is intuitively good, as it helps minimize the distance between the [conic/sphere] surfaces enclosing a country.
I found the answer looking through the repository - the tool is right there!
clone d3.js from the github repository.
edit /d3/examples/albers.html line 53 to point at your GEOJSON file:
Put the origin long / lat sliders to the center of your country / region (for me, it was 134° / 25°)
Change the paralells to be as close to the edges of your country / region.
adjust scale & offset to a nice size & position.
There are similar tools for the other projections.
edit: The repository has changed (and is constantly changing), so I've created a gist to preserve the example: https://gist.github.com/4552802
The examples are no longer part of the github repository.
My Question is as below in two parts……
QUESTION (IN SHORT):
• To generate point cloud of real-world object….
• Through 360 degree rotation of it….on rotating table
• Getting 360 images… one image at each degree (1° to 360°).
• I know how to process image and getting pixel value of it.
• See one sample image below…you can see image is black and white...because I have to deal with the objects which are much shiny (glittery)…and it is DIAMOND. So I have setting up background so that shiny object (diamond) converted in to B/W object. And so I can easily scan outer edge of object (e.g. Diamond).
• And one thing to consider is I don’t using any laser… I just using one rotating table and one camera for taking image…you can see one sample project over here… but there MATLAB hides all the things…because that guy using MATLAB’s in Built functionality.
• Actually I am looking for Math routine or Algorithm or any Technique which helping me out to how getting point cloud…….using the way I have mentioned……..
MORE ELABORATION:
I need to have point-cloud of real-world object. So, I can display it in Computer Screen.
For that I am using one rotating table. I will put my object on it and I will rotate table a complete 360° degree rotation and I will take 360 images…one image at each degree (1° to 360°).
Camera which is used for taking image is well calibrated. I have given one sample image as below. I also know how to scan image and getting pixel value of it.
Also take in consideration that my images are Silhouette type…means just black and white... No color images.
But my problem is or where I am trapped down is in...
Getting Points cloud of object…….from the data which I have getting through processing of image.
One same kind of project I found over here……..
But it just using built in MATLAB functions…I am using Microsoft Visual C#.Net so I have to build the entire algorithm myself….because MATLAB hides all the things which I want to know….
Is there any master…….who know this entire thing well and getting me out of trap...!!!!
Thanks…..
I have no experience of this but If I wanted to do something like this I would have tried this:
Use a single color light source
if Possible create a lightsource which falls on a thin verticle slice of the object.
have 360 B/W Images, those Images will be images of a verticle line having variyng intensity. If you use matlab your matrix will have a/few column with sime values.
now asume a verticle line(your Axis of rotation).
5 plot or convert (imageno, rownoOfMatrix, ValueInPopulatedColumnInSameRow)... [Assuming numbering Image from 0 to 360]
under ideal conditions A lame way To get X and Y use K1 * cos imgNo * ValInCol and K1 * sin imgNo * ValInCol, and Z will be some K2 * rowNum.. K1 and K2 can be caliberated knowing actual size of object.
I mean Something like this:
http://fab.cba.mit.edu/content/processes/structured_light/
but instead of using structured light using a single verticle light
http://www.geom.uiuc.edu/~samuelp/del_project.html This link might help in triangulation...