Querying https://nationalmap.gov/epqs to query for elevations make them available offline. Later on folks can specify a lat-long and can get it from the offline store.
The way I'd like to do this is to snap a given coordinates to a 10ft grid (or 100ft grid or whatever). So I'd prequery all values on the grid and store them, then when the offline query comes I can snap the request lat/long to the grid and just lookup the relevant value.
The problem is that I'd like my grids to be homogenized, that is that if two grids overlapped then their points would overlap if that makes sense. So I need a standardized offset for each grid so they all line up. Any ideas on how to achieve that?
I hope this makes sense.
Related
I have 19451 points exported by coordinates in a JSON file. I am trying to render them in an efficient way on the map with circles. How can I achieve this? It is the first time I am using https://github.com/react-native-maps/react-native-maps with expo, so I am not that experienced in using maps services. I don't even know where to start from. I was thinking of something like rendering the points dynamically, based on whether one point is to be found in the region of the map that is currently shown on the screen, although I have no idea how to actually achieve this. The first thing I tried was to obviously render them at once: it takes ages and it is very buggy!
You have several options:
Use some kind of clustering when there are multiple circles in the same area, for example when you're zoomed out. Have a look at react-native-maps-clustering. Performance wise is decent enough but it may lag on older devices.
When you go over a zoom level you can limit the number of circles you draw, I guess they overlap anyways. When your limit has been reached, you can display some warning to let the user know that the number of circles was limited and he should zoom in. From my experience, drawing max 50 custom markers was the upper limit to avoid lag on older devices. With circles, that limit might be different.
Manually filter your data and decide whether the circle belongs to the current viewport (visible part of the map) or not.
Some code would help me to give you some more hints.
I apologize in advance for my English.
I have in the application of more than 5000 coordinates.
These coordinates point to the objects in all the earth.
The fact that I add all at once to the map coordinates (marker), and the map is very lag because of this!
5-6 FPS when scrolling the map.
How do I add markers for the current location (the camera), and if I scroll the map, these markers to remove, and add new to the new location (the camera).
I know there is a function idleAtCameraPosition, but how to get a list of coordinates of the array (MutableArray), which is included in the camera? How to keep track of it?
I do not understand this. Can someone already did one of you is in your project?
I hope you understand that I want to convey to you.
You might want to check Marker Clustering:
By clustering your markers, you can put a large number of markers on a map without making the map hard to read. The marker clustering utility helps you manage multiple markers at different zoom levels.
When a user views the map at a high zoom level, the individual markers show on the map. When the user zooms out, the markers gather together into clusters, to make viewing the map easier.
To have some insights about loading too many marker, try reading the article about Too Many Markers!
Some applications are required to display a large number of locations or markers. Naively plotting thousands of markers on a map can quickly lead to a degraded user experience. Too many markers on the map cause both visual overload and sluggish interaction with the map. To overcome this poor performance, the information displayed on the map needs to be simplified.
Hope this helps!
I'm trying to build a descending graph in Cytoscape. I've got the majority done quite well, but now I'm stuck on the edge types. I'd like to use something like the 'segments' curve-style, where my edges have points.
However, instead of being zig-zags, I would like the edges to be constrained to horizontal/vertical lines.
My graph is pretty constrained and the user cannot manipulate the positions. I would like the edges to start at the 'parent' element, go straight down a set amount, then hit a point, turn, head horizontally to the same X as the child, then straight down to the child element.
Right now, the lines go straight, and I can add segments easily, but they aren't constrained and are based on percentages that I won't have access to without doing a bunch of math, which I guess isn't terrible.
Current:
Desired:
If you want specific absolute positions on segments edges, you'll need to convert the absolute co-ordinates to the relative co-ordinates that you specify for segments edges.
If you want a different type of edges for your usecase, feel free to propose it in the issue tracker.
I would like to know what is the recommended way of designing a Silverlight page with many controls in it, like a lob application for example. What I think would be simpler, especially if there are many pages to make, is to make a template page with a large number of rows and columns of the same dimension, so that I can visually put every control into the grid. In this way, each control will have something like absolute coordinates, as well as rowspan and columnspan.
Isn't this one the easiest way to design? I think such a layout would also be easier to modify, since if I want to move a textbox from the left to the right side of the screen, I only have to change it's Grid.Column property, without minding all the interactions with the stackpanels and the grids on the right side, like I see in many layouts that are organized with a number of grids and stackpanels.
And can the fact of having a large number of rows and columns decrease the performances?
Thanks for any opinion.
You can use a Canvas control if you want to do absolute positioning.
I am in the process of making my 2D engine for a Beat'em Up game (Castle Crashers is what I call Beat'em Up or Brawler kind of game ).
I will support 2D sprites and 2D particle emitters. This is all done in the engine now. But I have come to an issue that I would like to ask for advice:
It's about "space" management, what I thought was to do something as this image shows:
alt text http://img337.imageshack.us/img337/9162/spacingprototype1.png
My idea is to make a grid ( Spatial Hash or Grid ), of the ground where my Particle Emitters / 2D sprites will live. In my picture, I have enumerated this slots from 1 to N, (don't have to be 35, it's just for showing purposes ). My idea is to draw the "GameElements" (Sprites/Emitters) in order from 0 to N , ( going from bucket 0 to bucket N ) , so then I will get them to display correctly overlapped on screen (back to forward).
I know this could be done by just comparing the lower Y axis of each Element and performing a "quicksort" too, but having the Grid could allow me to perform Collision Detection in a better way , and if I do something like A* to implement some kind of AI, it could help me too.
If you want to have some sort of optimization for the number of objects you need to test against each other, you might want to think about using a Quadtree
http://en.wikipedia.org/wiki/Quadtree
The idea is to divide the screen up in 4 nodes, placing all items in the node they belong, then divide the nodes you just created up in another 4 if there are sprites/items/whatever in there that need to be tested. Keep doing this until a certain size or amount of items in a node has been reached.
You can then ask the top-node if it contains the item you want to test. This node will then ask the child-nodes if it contains the item, which in their turn will ask their children. This way a large part of the screen can be skipped already (if it's located in child 00, you can skip child 01, 10 and 11). Then you get a list of items you perform more specific collision detection on when it's desired to do so.
If you were to make it visual, it would look a bit like this:
alt text http://geodata.ethz.ch/geovite/tutorials/L2GeodataStructuresAndDataModels/en/images/quadtree.gif
Fire them out to the Z buffer and let that worry about it.
If you find that in the future it is too slow (via profiling obviously) then look at optimizing it.
Take the simplest solution and move on.
Your method fails if you have two sprites occupying the same box in the grid. Suppose you have two enemies both standing in the same box. One stands slightly in front of the other. Which do you draw first? You would need two algorithms - one which divides the sprites into the grid, and the second which looks at the z co-ordinates of all the sprites in a given grid box and draws them based on that value.
A far simpler method is to have a single collection of all sprites. It should store all sprites sorted by their z co-ordinates (from the back of the screen at the head of the list to the front of the screen at the back). Loop through the collection and draw each sprite as it appears. When a sprite moves into or out of the screen (ie. its z co-ordinate changes) you can perform a very simple sort to move that single sprite within the collection. Keep swapping it with the next sprite in the list until the next sprite's z co-ordinate is greater than/less than (as appropriate) the changed sprite's co-ordinate.