One afternoon at Java City, my friend Eric and I were discussing about the ways to to get raster pixel values along the overlaying line. The conversation encourages me to write an quick and dirty solution to solve the issue. The following R code snippet helps to conceive an idea to extract the raster values which are intersect or touch by the overlaying straight line in easy fashion using R raster package.
#Print the raster pixel values along the overlaying line in R. The line's start and end row/col (coordinates) must be provided.
library(raster)
#Create an arbitrary raster, for instance I used a names of color as raster pixel values.
r <- as.raster(matrix(colors()[1:100], ncol = 10))
#Start coordinate of a sample line
x0=1 #row = 1
y0=3 #column = 3
r[x0,y0]
#End coordinate of a sample line
x1=10 #row =10
y1=7 #column=7
#Easy sample line generation algorithm : A naïve line-drawing algorithm
dx=x1-x0
dy=y1-y0
for( x in x0:x1)
{
y = y0 + (dy) * (x - x0)/(dx)
#Print the raster pixel values along the line
print(r[x,y])
}
Pretty simple concept. You can tweak the code & the line drawing algorithm as your requirement. There are several line drawing algorithm available in the internet. Here I used a simplest one that I found.
Monday, June 10, 2013
Tuesday, May 21, 2013
Generate Euclidean distance matrix from a point to its neighboring points in R
#Generate Euclidean distance matrix from a point to its neighboring points in R
#Load sp library
library(sp)
#Create a 2D metrix of X & Y coordinates of the neighboring points
neighbours_point <- matrix(c(5, 6,3,5,4,8,7, 10, 60, 60,11,12), ncol=2)
neighbours_point
[,1] [,2]
[1,] 5 7
[2,] 6 10
[3,] 3 60
[4,] 5 60
[5,] 4 11
[6,] 8 12
#Create a point vector with x and y coordinates from which distance should be calculated
refrence_point<-c(2,3)
refrence_point
[1] 2 3
#Compute the distance matrix
distmat <- spDistsN1(neighbours_point,refrence_point, longlat=FALSE)
distmat
[1] 5.000000 8.062258 57.008771 57.078893 8.246211 10.816654
Enjoy!!
Monday, April 29, 2013
Call for Presentations
The Annual Missouri Mappers Conference will be held
July 23 - 26 at Tan-Tar-A Resort at
Osage Beach, MO.
Go to www.MissouriMappers.org to learn more about us!
We are changing our format up a bit and will hold even more workshops and break-out sessions this year! We are looking for presenters willing to do 30 or 45 minute presentations.
Examples of prior conference topics include: Property Assessment & Mapping (Pen & Ink or Digital), Emergency Management, Deed Interpretation, Mobile/GPS, topics concerning local governments and mapping.
This promises to be an awesome conference in a brand new location so come share with us!. Please contact the Conference Chair Lisa Perry at lisap@ecarthage.com for information and time slots.
Monday, April 8, 2013
Free GIS and 911 Seminar
Mid-AmericaGIS Consortium (MAGIC) has teamed up with GeoComm, St. Clair IL, and WashingtonUniversity St. Louis to offer a FREE E911 and GIS Seminar in St. Louis, MO on
May 29, 2013.
This
workshop is for folks working on 911 system and GIS data. This seminar will
help build the foundation for understanding requirements, roles, responsibilities,
and standards for present 911 systems and NEXT GENERATION 911.
This
one day seminar will cover:
·
911
and GIS today
·
Developing
communication between 911 and GIS professionals
·
Where
is 911 going and what are the new GIS functions?
·
NENA
GIS model for public safety
·
Roadmap
to future GIS requirements
Date
and Location
May 29, 2013 (9:00 am-4:00pm),
Washington University-West Campus
7425 Forsyth Blvd. St. Louis. MO
63105
Accommodations
Sheraton Clayton Plaza Hotel, St.
Louis
Registration is FREE.
For more information, and to
register:
Tuesday, March 26, 2013
Friday, March 22, 2013
First Image of Earth from LandSat 8
According to NASA website, LDCM’s first instrument,
Operational Land Imager, or OLI instrument, that took the natural color image.
The natural color image showed the landscape in the colors our eyes would see,
but Landsat sensors also have the ability to see wavelengths of light that our
eyes cannot see. LDCM sees eleven bands within the electromagnetic spectrum,
the range of wavelengths of light. OLI collects light reflected from Earth's
surface in nine of these bands. Wavelengths on the shorter side include the
visible blue, green, and red bands. Wavelengths on the longer side include the
near infrared and shortwave infrared. LDCM's second instrument, the Thermal InfraredSensor (TIRS) detects light emitted from the surface in two even longer
wavelengths called the thermal infrared. The intensity of the emitted light at
the longer wavelengths measured by TIRS is a function of surface temperature.
Good Book for GIS Beginners : Book II
Understanding GIS: An ArcGIS Project Workbook, is a very user-friendly written book for those interested to begin using ESRI ArcGIS Desktop 10 or ArcGIS Desktop 10.1 using real data from the City of Los Angeles' Department of Public Works, Bureau of Engineering's Mapping Division, and Department of Recreation and Parks and to manipulate it using the power of GIS.
Don't expect to become a GIS expert at the end because this is simply a good introduction to ArcGIS. The book guides the reader step-by-step, mouse-click-by mouse-click, decision-by-decision through a GIS project to determine for yourself which locations along the river are best suited for public recreational use in Los Angeles. At the end, you will have learned many of the fundamentals of GIS generally and ArcGIS specifically which aims at finding a suitable land parcel(s)for a new park area in Los Angeles .You use real data which comes in the companion DVD. When you reach the final stage in chapter 6 and follow all the careful steps to manually select the best areas and you learned why you do so, you discover in the following chapter (chapter 7) that you can do the same in a much quicker way by using a visual graphing tool, a marvel in my opinion of ArcGIS Desktop.
Wednesday, February 27, 2013
GeoExt Layer Tree: Showing BaseLayers and Overlay Layer
I was looking for GeoExt's tree example for my project, and I found official tutorials are kind of hard to understand for the GeoExt beginners. On Googleing through the internet, I found nice and easy way of creating tree structure menu using GeoExt BaseLayer and Overlay layer tree.
Tuesday, February 26, 2013
Geography of Pizza : Trying to Explore VGI and Crowd Sourcing
He classified pizzas by:
- Style
- Crust
- Cheese
- Sauce
- Toppings
- Sold by
- Slices Cut
- Oven
Friday, February 22, 2013
Geographic Information Science (GIS) Internships Summer 2013
Title
|
Location
|
Requirement
|
Click Link for Details
|
Summer 2013 Internship
|
Burlington, Vermont
|
GIS Mapping Project - This internship includes a stipend of $4,000 for 10 weeks work.
|
|
GIS Intern
|
Anchorage, AK
|
-Knowledge of Esri ArcGIS software, GIS analysis, ---Microsoft Outlook, Microsoft Office suite. Knowledge of AutoCAD/Microstation is a plus.
|
|
GIS Intern
|
Oakland, CA
|
Currently enrolled as a junior or senior in Geography or related field.
- Intermediate skills using Esri ArcGIS version 10 - Good written and communication skills. |
|
Intern - GIS Summer
|
Madison,WI
|
-Demonstrated working knowledge of ESRI data formats and Microsoft Office products
-Must have a minimum of one year undergraduate education in GIS, Cartography, or other related discipline and be currently enrolled in and actively working towards a degree
|
|
Horticulture & GIS Interns
|
Missouri Botanical Garden, MO
|
Various Openings
|
|
GIS Intern
|
Boston, MA
|
-College Graduate BA/BS
-Understanding of excel and economic modeling a plus.
|
|
12-Week GIS Internship
|
National Park Service , Gatlinburg, TN
|
-Experience in geographic information systems (GIS), computer cartography a must, specifically experience using ArcGIS Desktop (ArcMap/ArcCatalog). Experience with geodatabase formats is a plus.
|
|
GIS Intern
|
Arlington, TX
|
Skill in Arc GIS, Arc GIS editing environment and Geo-processing tools is essential.
|
|
GIS Intern
|
Southlake, Texas
|
-Work requires knowledge of a specific vocational, administrative, or technical nature that may be obtained with advanced study or training past the high school equivalency.
|
|
Environmental Intern
|
-Proficiency with GIS software preferred.
-Must be enrolled in a planning program in an accredited School of Planning
|
| |
Intern II
|
Philadelphia, PA
|
-Bachelors or Master’s degree complete or in progress
-Experience with GIS, simple web design, and graphic design a plus
|
|
Wildfire Planning Intern
|
North Carolina
|
-Undergraduate or graduate program focusing on Environmental Studies, Biology, Forestry, or related field
-Ability to perform physical work, sometime under adverse conditions or in inclement weather
-Ability to make maps using GIS
|
|
GIS Intern
|
Libertyville, Illinois
|
-Knowledge of geography as applied to concepts and principles of GIS, map projections and datums, coordinate systems and cartographic designs.
-Ability to use GIS equipment, instruments and devices
|
|
GIS Coordinator Intern
|
Sioux Falls,SD
|
-Working knowledge of ESRI and ArcGIS software
-Knowledge of GPS or GPS/GIS data collection.
-Knowledge in CAD and design software.
|
|
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