December 17, 2017

How to Convert a Matrix in a Geospatial Tiff in QGIS with PyQGIS - Tutorial

December 17, 2017/ Saul Montoya

Raster are matrices with geospatial reference. In order to make a finite difference model or any other model compatible with QGIS we have to process the matrix with its parameters to be represented as a spatially referenced raster. The process involves some Python scripting on the QGIS console, processing time is low and the process can be applied for many matrices without visual representation of intermediate files that saves computational time and resources.

This tutorial show the complete process of matrix construction, parameter calculation and spatially representation in the Python console of QGIS.

December 16, 2017

How to convert GTIFF to STL for Topography Representation in OpenFOAM Models

December 16, 2017/ Saul Montoya

For OpenFOAM modelers the representation of topography can be painful due to the unstabilities and complexities of the Bezier Surfaces in Salome Platform. It is more stable to create the mesh by importing a full textured surface on a format file compatible with Salome. This tutorial show the process to create a STL file from a GeoTiff(.tif) file by scripts in Python. We have used the OSGeo4W Shell that comes with the normal QGIS instalation because it comes with the gdal library already installed.

December 15, 2017

How To Create Line From Points in QGIS with PyQGIS and Pandas - Tutorial

December 15, 2017/ Saul Montoya

Python scripting allows us to enhance the data management and spatial analysis in QGIS. Most times, spatial data comes from a variety of data providers in a sort of formats and data types that we have to be adapted to the GIS standard. Big data and continuos monitoring create large datasets that have to indexed, sorted and manipulated in a effective way.

QGIS has a Python console and the capability to install external Python packages that run on QGIS session. This time we have installed Pandas in QGIS to handle the data from a sensing device made on a Raspberry Pi 3 and then we have defined the path as a succession of points with PyQGIS scripting.

December 12, 2017

Spatio-Temporal Hurricane Tracking in the Gulf of Mexico with QGIS and PyQGIS - Tutorial

December 12, 2017/ Saul Montoya

This tutorial show a mixed procedure with native QGIS tools and PyQGIS commands for the data representation, styling and plotting with spatio-temporal criteria with the TimeManager plugin. Data for this tutorial was downloaded from the National Hurricane Center's Tropical Cyclone Reports that contains information as six-hourly positions and intensities. You can access the whole hurricane database o

December 12, 2017

How to add multiple Vector Layers and group them in QGIS with PyQGIS - Tutorial

December 12, 2017/ Saul Montoya

QGIS is a great software for the processing/analysis of spatial data, Python is a clear, powerful programming lenguaje; together they can enhance the spatial analysis to solve more complex or more dedicated problems in less time. PyQGIS is the Python environment inside QGIS with a set of QGIS libraries plus the Python tools with the potential of running other powerful libraries as Pandas, Numpy or Scikit-learn.

This tutorial shows the whole procedure to upload multiple files from a certain pattern and group them on the Layer Panel using PyQGIS commands.

December 10, 2017

How to Upload a Shapefile in QGIS with PyQGIS - Tutorial

December 10, 2017/ Saul Montoya

December 04, 2017

Tree / Crop Counting and Classification with Python and Scikit-Image - Tutorial

December 04, 2017/ Saul Montoya

Lately there has been a wide source of spatial photogrametry available for agriculture. Available submetric images can be found in Google Earth, and drone images can increase the ortophoto resolution to the order of centimeters. Most of this data gives us a new perspective of the spatial distribution and stage of the crops, however a real spatial analysis of crop metrics have not been widely performed due to limitations on the images and software involved.

We tried to make this tutorial with the popular library OpenCV, however the installation process was tedious in Windows. Then we shifted to Scikit-Image, a image processing library in Python that comes already installed on the Anaconda software. The process for image analysis required intermediate Python and GIS skills, but most important a strong criteria of the algorithm inputs, options and results.

December 02, 2017

How to join tables in QGIS - Tutorial

December 02, 2017/ Saul Montoya

QGIS is a powerful open source software for spatial analysis and management of spatial data. User experience with QGIS is great and most users find QGIS easier to use than other free and commercial GIS software. This time we will show how simple is the process to join tables in QGIS. Spatial data of sanitary quality of beaches in Lima was used to show the join table process.

December 01, 2017

Groundwater Flow Simulation at Mine Closure Time Scale with MODFLOW and Model Muse

December 01, 2017/ Saul Montoya

This tutorial deals with the simulation of the groundwater flow regimen after the implementation of mine closure options as soil/geomembrane cover above a Tailings Storage Facility (TSF) over a period of 80 years with results every 4 years. The tutorial deal with a full steady flow model which have been implemented to transient conditions on the model configuration and boundary conditions. A discussion of the seepage with time and final conditions after closure is presented to analyse the efficiency of the closure techniques.

November 29, 2017

Example of Zone Budget Package in MODFLOW with Model Muse

November 29, 2017/ Saul Montoya

MODFLOW is the code developed by the USGS for the simulation of groundwater flow in steady and transient flow conditions. MODFLOW can represent a wide variety of physical process related to the groundwater flow regime as recharge, evapotranspiration, wells, among others. Latest development in MODFLOW allow the simulation of flow and transport in the unsaturated flow zone with the UZF and MT3D packages. From the beginning of the MODFLOW development the water balance on the groundwater models was a strong part of the modeling process with high accuracy in between the balance of water going in and out of the system. On any groundwater flow model build on MODFLOW there absolutely control over the water coming from the specified boundary conditions and the discrepancies are minimal.

November 23, 2017

Pathline Simulation of Seepage Flow from a Tailings Dam with MODFLOW & MODPATH - Tutorial

November 23, 2017/ Saul Montoya

Due to their extension and climate conditions, Tailings Storage Facilities (TSF) are in interaction with groundwater flow having a dual behaviour of discharge and recharge zones. Long term evaluation of environmental impact from tailings have to consider the potential impact from the leachates into the groundwater flow regime and the impact on water quality on the downstream channels. Numerical modeling is a strong tool for the evaluation of flows and quality on the overall impact zone from tailings dam in current and future conditions.

Simulations on mine closure last for decades, and several remediation techniques as infiltration ponds, pump and test schemes, reactive walls have to be simulated on the long term. This tutorial show the procedure to simulate the particle tracking of seepage flow from tailings and estimate the potential affected stream network. The tutorial also discuss some common problems in the particle tracking simulation.

Modeling work was done in MODFLOW with Model Muse on steady state conditions over a 5 layer model with 101260 cells.

November 16, 2017

Example of Particle Tracking Modeling with MODPATH in Model Muse

November 16, 2017/ Saul Montoya

MODPATH is a particle tracking model that runs on the groundwater flow models simulated on MODFLOW. Particle tracking are three dimensional and can have a sort of options as forward / backward modeling direction in between others. Model Muse is a pre and post-processor of numerical models in MODFLOW, PHAST and SUTRA, this software can simulate some MODFLOW related models as MODPATH and MT3D (particle tracking and mass transport respectively). This tutorial show the basic procedure to set up a particle tracking model with MODPATH using Model Muse over a basic MODFLOW model.

November 04, 2017

What is the relevance of confined / unconfined aquifer type on groundwater flow?

November 04, 2017/ Saul Montoya

Maybe confined or unconfined aquifer are terms that would sound familiar from your first hydrogeology class, however it´s a simple definition about the location of the hydraulic head over the vertical limits of your aquifer. It might be that you have employed those terms in different reports, or maybe you have seen this aquifer classification on some environmental impact assessments or geological reports, but which is the relevance of this classification on the groundwater flow? This article talks about the comparison of the the confined / unconfined aquifer condition based on numerical modeling with some discussion about the convertible character of the aquifer.

November 02, 2017

Introduction to PyQGIS, the Python environment in QGIS

November 02, 2017/ Saul Montoya

October 30, 2017

Tutorial: Georeferencing Historic/Ancient Maps with QGIS

October 30, 2017/ Saul Montoya

Working with spatial data on many environments requires an historic perspective of the land use, urban development and other changes on earth surface. Some times (or most times) the only data available is on printed form with or without a system of reference that makes this data of limited use for a spatial analysis. Afortunately, QGIS can handle the georeferenciation of ancient maps on a smooth and quick way based on the functionality of its tools.

Anyone can overlay an historic map on the map canvas on few steps. This tutorial shows the whole procedure to georeference a map of Lima city from 1856 in QGIS.

October 27, 2017

Tutorial: Wave Barrier Design with OpenFOAM and Salome

October 27, 2017/ Saul Montoya

Coastal structures are subject to tidal and wave related boundary conditions. The design of a wave barrier have to assess the water levels on the inner bay from the impact of a wave and the maximum wave height on the outside part of the structure. This evaluation can be done by the use of dynamic simulations that take into account sea floor geometry, wave barrier height, position and interaction from the water channel and so on. OpenFOAM is an open source software for the simulation of flow in steady and transient states; the software allows us the simulation of the wave interaction with the coastal structure. The tutorial deals with the main parts of mesh construction in Salome and model set up and simulation in OpenFOAM.

October 25, 2017

Tutorial: Determination of Glaciers and Lakes from Sentinel 2 Images with QGIS and SCP Plugin

October 25, 2017/ Saul Montoya

Any object on the earth has a "signature" on a different bands or ranges on the visible and invisible spectrum. Base on the values and trends on this "spectral signature" one can classify different types of land cover as lakes, soils, wetlands, exposed rock and glaciers from many free and available multispectral satellite images as Sentinel 2, Aster, MODIS, and Landsat. QGIS is a very powerful open geographical information system software and its plugin Semiautomatic Classification Plugin gives QGIS many capabilities for the download, preprocess, classification and analysis of satellite imagery without using another desktop software. This tutorial deals with the whole procedure for the supervised classification of lakes and glaciers on a clipped Sentinel 2 image and its vectorization as polygons.

October 19, 2017

Tutorial: Example Problem of MODFLOW with Model Muse

October 19, 2017/ Saul Montoya

This example problem is adapted from the MODFLOW documentation and use to demostrate the use of MODFLOW with Model Muse. The model is implemented without parameters and uses the LPF Package. The model decribes a regional aquifer setup with acuifers and aquitards with the interaction of many boundary conditions as recharge, evapotranspiration, constant head and wells. Groundwater flow simulation was done on steady state conditions.

October 19, 2017

Tutorial: Direct Landsat Imagery Dowload in QGIS with SCP Plugin

October 19, 2017/ Saul Montoya

Based on the review from our followers, we have noticed that the download procedure to download images from the NASA and USGS web servers had changed. It is not clear the current method to download the selected files, even if you have your username and password set up correctly. Luckly there is an alternative way to download those files with QGIS and the Semiautomatic Classification Plugin (SCP). This tutorial covers the whole procedure to sign up, select, previsualize and download a Landsat 8 in QGIS with the SCP Plugin.

October 17, 2017

Tutorial: Intake Channel Design with OpenFOAM and Salome

October 17, 2017/ Saul Montoya

The design of hydraulic structures need the comprehension of water and structure interaction in terms of level, speed, sediment transport, among others. It is important for the hydraulic structure design to take into account the extreme events of flow, pressure and speed, therefore the computational fluid dynamics (CFD) modeling becomes essential in the design stage. OpenFOAM is an open source software for the simulation of flow in steady and transient states; this software allows us the simulation of the hydraulic response from an specific requirement in laminar and turbulent flow conditions, flow velocity calculation, and determination of static and dynamic pressures.