Monday, February 29, 2016

Using Dropbox to Host your webmap

Dropbox, surprisingly could be used to host a static web page. There are other providers too like Google Drive. But its capabilities will be discontinued after August 2016. And by the this functionality, we can host a simple webmap (or little bit complex, I dont know, didnt test it yet) using this service.

The hosting procedure is quite easy,

1. Make a dropbox account and login

2. Looks for "Public" folder and make a directory there.

3. Write your own webmap, for example I copy an html file somewhere, and edit it to include my Mapbox webmap into its DIV Tag, then I just place the html to the directory created on step 2.

The code looks like this :

4. Save it to Html and place to the directory on the step 2.

5.  Then left clik on it, > Looks for "Copy Public Link"

6. Paste into browser.

7. Click this LINK to see how the code in step 3 looks like

Saturday, February 27, 2016

Surface Reflectance in ArcGIS

I just noticed that at the recent version, ArcGIS has been implemented some sort of physical liked surface reflectance generation function in its image analysis module. The function is called apparent surface reflectance. An algorithm which takes into consideration all the iradiance related information stored in the metadata (sun azimuth angle, sun elevation angle, radiance gain/bias etc) to derive surface reflectance dataset, although it is not pure physical (because it does not consider the atmospheric condition at the acquisition date). The algorithm target the illumination condition which is theoretically should be similar between dates and wavelengths (differs in reality due to atmospheric effects, sun angle/position and sun-earth distance in every season etc) so it could be usable for color balancing and mosaicking (not sure if it will add certain degrees of accuracy in image classification).

I make a guide if you want to try it by yourself

Sunday, February 14, 2016

Download Landsat 8 Data Using SnapSat.Org

A new landsat-8 data provider has been added
Using simple interface you can straightforwardly download landsat-8 data either just some bands or full dataset.
This portal utilizing Amazon S3 free access Landsat-8 repository, so it will have some data acquisition delay compared with official USGS repository (EarthExplorer, GLOVIS, REVERB).
Based on the test I conducted, I think data access thru this portal is greatly useful if you just need some quicklook or visual interpretation needs.
Oh btw, Landsat-8 data obtained from this portal is reprojected to Web Mercator Projection, so if you need the data in UTM or Geographic Projection, just reproject it using ArcGIS, QGIS or other Geospatial softwares.

Saturday, February 6, 2016

Creating Simple Web Map Using QGIS

From day to day, QGIS is getting bigger and bigger. Continuous and expanded support from open source geospatial developer has made this software go beyond its initial development. More and more tools/plugins has been created and offering more flexibility and features to the software. It is fair to said that this software is now became an ideal example of successful non commercials geospatial movement. Personally I am starting to count more on this software because it is now offering some distinct tools unavailable on commercial counterparts. The keys of QGIS for me are simplicity, straightforward how to, and free to use.

I am not kidding, below is an example how the simplicity means. A Tutorial about how Online Map could be deployed easily from QGIS. Using fast growing to use WebMap Frameworks like Openlayers or leaflet, a not experienced and programming literate user could make an online webmap with sophisticated looks just with some clicks. Check it out below.

And last but not least, innovation is not coming from the "follow the leader" attitude (IFYWIM) :P