I'm trying to calculate average rainfall value from a number of points using Inverse Weighted Distance tool in ArcGIS 9.3.
My problem is that: each point has it own time series, therefore the interpolation process should be able to carry out for all years (kind of iteration so to speak).
Following is a sample attribute table:
ID X Y Name Rain1990 Rain1991 Rain1992 Rain1993 .... Rain2010
1 xx1 yy1 AA 1210 1189 1863 1269 ......
2 xx2 yy2 BB 1492 1502 2187 1923 ......
......
Could anybody show me how to do that?
Edit 1: I finally did this by using C++ code which required ArcGIS mask grid, data files & locations of all the points.
Edit 2: I recently used R to do this interpolation task. You can use either hydroTSM
, gstat
or spacetime
packages. Few example links below:
http://spatial-analyst.net/wiki/index.php?title=Spatial_interpolation_exercises_%28NL%29
http://www.geostat-course.org/Topic_Bivand_2012
Edit 3: Added a working example below for future readers
Answer
Add my own solution using R
& random precipitation data
library(tidyverse)
library(sp) # for coordinates, CRS, proj4string, etc
library(gstat)
library(maptools)
# Coordinates of gridded precipitation cells
precGridPts <- ("ID lat long
1 46.78125 -121.46875
2 46.84375 -121.53125
3 46.84375 -121.46875
4 46.84375 -121.40625
5 46.84375 -121.34375
6 46.90625 -121.53125
7 46.90625 -121.46875
8 46.90625 -121.40625
9 46.90625 -121.34375
10 46.90625 -121.28125
11 46.96875 -121.46875
12 46.96875 -121.40625
13 46.96875 -121.34375
14 46.96875 -121.28125
15 46.96875 -121.21875
16 46.96875 -121.15625
")
# Read precipitation cells
precGridPtsdf <- read.table(text = precGridPts, header = TRUE)
Convert to a sp object
sp::coordinates(precGridPtsdf) <- ~long + lat # longitude first
Add a spatial reference system (SRS) or coordinate reference system (CRS).
# CRS database: http://spatialreference.org/ref/epsg/
sp::proj4string(precGridPtsdf) <- sp::CRS("+proj=longlat +ellps=WGS84 +datum=WGS84")
str(precGridPtsdf)
#> Formal class 'SpatialPointsDataFrame' [package "sp"] with 5 slots
#> ..@ data :'data.frame': 16 obs. of 1 variable:
#> .. ..$ ID: int [1:16] 1 2 3 4 5 6 7 8 9 10 ...
#> ..@ coords.nrs : int [1:2] 3 2
#> ..@ coords : num [1:16, 1:2] -121 -122 -121 -121 -121 ...
#> .. ..- attr(*, "dimnames")=List of 2
#> .. .. ..$ : chr [1:16] "1" "2" "3" "4" ...
#> .. .. ..$ : chr [1:2] "long" "lat"
#> ..@ bbox : num [1:2, 1:2] -121.5 46.8 -121.2 47
#> .. ..- attr(*, "dimnames")=List of 2
#> .. .. ..$ : chr [1:2] "long" "lat"
#> .. .. ..$ : chr [1:2] "min" "max"
#> ..@ proj4string:Formal class 'CRS' [package "sp"] with 1 slot
#> .. .. ..@ projargs: chr "+proj=longlat +ellps=WGS84 +datum=WGS84 +towgs84=0,0,0"
Convert to UTM 10N
utm10n <- "+proj=utm +zone=10 ellps=WGS84"
precGridPtsdf_UTM <- spTransform(precGridPtsdf, CRS(utm10n))
Hypothetical annual precipitation data generated using Poisson distribution.
precDataTxt <- ("ID PRCP2016 PRCP2017 PRCP2018
1 2125 2099 2203
2 2075 2160 2119
3 2170 2153 2180
4 2130 2118 2153
5 2170 2083 2179
6 2109 2008 2107
7 2109 2189 2093
8 2058 2170 2067
9 2154 2119 2139
10 2056 2184 2120
11 2080 2123 2107
12 2110 2150 2175
13 2176 2105 2126
14 2088 2057 2199
15 2032 2029 2100
16 2133 2108 2006"
)
precData <- read_table2(precDataTxt, col_types = cols(ID = "i"))
Merge Prec data frame with Prec shapefile
precGridPtsdf <- merge(precGridPtsdf, precData, by.x = "ID", by.y = "ID")
precdf <- data.frame(precGridPtsdf)
Merge Precipitation data frame with Precipitation shapefile (UTM)
precGridPtsdf_UTM <- merge(precGridPtsdf_UTM, precData, by.x = "ID", by.y = "ID")
# sample extent
region_extent <- structure(c(612566.169007975, 5185395.70942594, 639349.654465079,
5205871.0782451), .Dim = c(2L, 2L), .Dimnames = list(c("x", "y"
), c("min", "max")))
Define the extent for spatial interpolation. Make it 4km larger on each direction
x.range <- c(region_extent[1] - 4000, region_extent[3] + 4000)
y.range <- c(region_extent[2] - 4000, region_extent[4] + 4000)
Create desired grid at 1km resolution
grd <- expand.grid(x = seq(from = x.range[1], to = x.range[2], by = 1000),
y = seq(from = y.range[1], to = y.range[2], by = 1000))
# Convert grid to spatial object
coordinates(grd) <- ~x + y
# Use the same projection as boundary_UTM
proj4string(grd) <- "+proj=utm +zone=10 ellps=WGS84 +ellps=WGS84"
gridded(grd) <- TRUE
Interpolate using Inverse Distance Weighted (IDW)
idw <- idw(formula = PRCP2016 ~ 1, locations = precGridPtsdf_UTM, newdata = grd)
#> [inverse distance weighted interpolation]
# Clean up
idw.output = as.data.frame(idw)
names(idw.output)[1:3] <- c("Longitude", "Latitude", "Precipitation")
precdf_UTM <- data.frame(precGridPtsdf_UTM)
Plot interpolation results
idwPlt1 <- ggplot() +
geom_tile(data = idw.output, aes(x = Longitude, y = Latitude, fill = Precipitation)) +
geom_point(data = precdf_UTM, aes(x = long, y = lat, size = PRCP2016), shape = 21, colour = "red") +
viridis::scale_fill_viridis() +
scale_size_continuous(name = "") +
theme_bw() +
scale_x_continuous(expand = c(0, 0)) +
scale_y_continuous(expand = c(0, 0)) +
theme(axis.text.y = element_text(angle = 90)) +
theme(axis.title.y = element_text(margin = margin(t = 0, r = 10, b = 0, l = 0)))
idwPlt1
### Now looping through every year
list.idw <- colnames(precData)[-1] %>%
set_names() %>%
map(., ~ idw(as.formula(paste(.x, "~ 1")),
locations = precGridPtsdf_UTM, newdata = grd))
#> [inverse distance weighted interpolation]
#> [inverse distance weighted interpolation]
#> [inverse distance weighted interpolation]
idw.output.df = as.data.frame(list.idw) %>% as.tibble()
idw.output.df
#> # A tibble: 1,015 x 12
#> PRCP2016.x PRCP2016.y PRCP2016.var1.pred PRCP2016.var1.var PRCP2017.x
#> *
#> 1 608566. 5181396. 2114. NA 608566.
#> 2 609566. 5181396. 2115. NA 609566.
#> 3 610566. 5181396. 2116. NA 610566.
#> 4 611566. 5181396. 2117. NA 611566.
#> 5 612566. 5181396. 2119. NA 612566.
#> 6 613566. 5181396. 2121. NA 613566.
#> 7 614566. 5181396. 2123. NA 614566.
#> 8 615566. 5181396. 2124. NA 615566.
#> 9 616566. 5181396. 2125. NA 616566.
#> 10 617566. 5181396. 2125. NA 617566.
#> # ... with 1,005 more rows, and 7 more variables: PRCP2017.y ,
#> # PRCP2017.var1.pred , PRCP2017.var1.var , PRCP2018.x ,
#> # PRCP2018.y , PRCP2018.var1.pred , PRCP2018.var1.var
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