ee.Image.reproject

فرض احتساب صورة في إسقاط ودقة محدّدين

الاستخدام	المرتجعات
Image.reproject(crs, crsTransform, scale)	صورة

الوسيطة	النوع	التفاصيل
هذا: image	صورة	الصورة المطلوب إعادة عرضها.
crs	الإسقاط	نظام الإحداثيات المرجعي الذي سيتم عرض الصورة عليه.
crsTransform	قائمة، القيمة التلقائية: فارغة	قائمة بقيم تحويل نظام الإحداثيات المرجعية (CRS). هذا ترتيب رئيسي للصف لمصفوفة التحويل 3x2. لا يمكن استخدام هذا الخيار مع خيار المقياس، ويحلّ محلّ أي عملية تحويل تم إجراؤها على العرض.
scale	العدد العائم، القيمة التلقائية: null	في حال تحديد المقياس، يتم تغيير حجم العرض عن طريق قسمة قيمة المقياس المحدّدة على الحجم الاسمي للمتر في العرض المحدّد. في حال عدم تحديد المقياس، سيتم استخدام مقياس الإسقاط المحدّد.

أمثلة

محرّر الرموز البرمجية (JavaScript)

// Use of ee.Image.reproject is rarely needed and should generally be avoided.
// Defining the projection and scale of analysis should be handled by "scale",
// "crs", and "crsTransform" parameters whenever they are offered by a function.
// It is occasionally useful for forcing computation or visualization at a
// desired scale and projection when alternative methods are not available. In
// this example it is used to compute and visualize terrain slope from a DEM
// composite.

// Calculate mean elevation from two DEM datasets. The resulting composite
// image has a default CRS of WGS84 with 1 degree pixels.
var dem1 = ee.Image('NASA/NASADEM_HGT/001').select('elevation');
var dem2 = ee.Image('CGIAR/SRTM90_V4').select('elevation');
var demMean = ee.ImageCollection([dem1, dem2]).mean();

// Display the DEMs on the map, note that they all render as expected.
var demVisParams = {min: 500, max: 2500};
Map.setCenter(-123.457, 47.815, 11);
Map.addLayer(dem1, demVisParams, 'DEM 1');
Map.addLayer(dem2, demVisParams, 'DEM 2');
Map.addLayer(demMean, demVisParams, 'DEM composite');

// Calculate terrain slope from the composite DEM (WGS84, 1 degree pixel scale).
var demCompSlope = ee.Terrain.slope(demMean);

// Because the composite has 1 degree pixel scale, the slope calculation
// is essenstially meaningless and difficult to even display (you may need to
// zoom out to see the individual 1 degree pixels).
Map.addLayer(demCompSlope, {min: 0, max: 0.3}, 'Slope');

// We can use ee.Image.reproject to force the slope calculation and display
// the result with a reasonable scale of 30 m on WGS84 CRS, for example.
var slopeScale = ee.Terrain.slope(
  demMean.reproject({
    crs: 'EPSG:4326',
    scale: 30
  })
);
Map.addLayer(slopeScale, {min: 0, max: 45}, 'Slope w/ CRS and scale');

// To more precisely control the reprojection, you can use the "crsTransform"
// parameter instead of the "scale" parameter or set the projection according to
// a reference image. For example, here the input composite image for the slope
// function is set to match the grid spacing and alignment of the NASADEM image.
var nasademProj = dem1.projection();
var demMeanReproj = demMean.reproject(nasademProj);
var slopeRefProj = ee.Terrain.slope(demMeanReproj);
Map.addLayer(slopeRefProj, {min: 0, max: 45}, 'Slope w/ reference proj');
print('Reference projection', nasademProj);
print('DEM composite projection', demMeanReproj.projection());

// An alternative method for changing the projection of image composites
// (not accepting the default WGS84 CRS with 1 degree pixel scale) is to
// explicitly set the default projection using ee.Image.setDefaultProjection,
// which will not force resampling, like ee.Image.reproject will.
var demMeanProj = ee.ImageCollection([dem1, dem2]).mean()
                      .setDefaultProjection(nasademProj);
var slopeProj = ee.Terrain.slope(demMeanProj);
Map.addLayer(slopeProj, {min: 0, max: 45}, 'slope w/ default projection set');

إعداد Python

راجِع صفحة بيئة Python للحصول على معلومات حول واجهة برمجة التطبيقات Python واستخدام geemap للتطوير التفاعلي.

import ee
import geemap.core as geemap

Colab (Python)

# Use of ee.Image.reproject is rarely needed and should generally be avoided.
# Defining the projection and scale of analysis should be handled by "scale",
# "crs", and "crsTransform" parameters whenever they are offered by a function.
# It is occasionally useful for forcing computation or visualization at a
# desired scale and projection when alternative methods are not available. In
# this example it is used to compute and visualize terrain slope from a DEM
# composite.

# Calculate mean elevation from two DEM datasets. The resulting composite
# image has a default CRS of WGS84 with 1 degree pixels.
dem_1 = ee.Image('NASA/NASADEM_HGT/001').select('elevation')
dem_2 = ee.Image('CGIAR/SRTM90_V4').select('elevation')
dem_mean = ee.ImageCollection([dem_1, dem_2]).mean()

# Display the DEMs on the map, note that they all render as expected.
dem_vis_params = {'min': 500, 'max': 2500}
m = geemap.Map()
m.set_center(-123.457, 47.815, 11)
m.add_layer(dem_1, dem_vis_params, 'DEM 1')
m.add_layer(dem_2, dem_vis_params, 'DEM 2')
m.add_layer(dem_mean, dem_vis_params, 'DEM composite')

# Calculate terrain slope from the composite DEM (WGS84, 1 degree pixel scale).
dem_comp_slope = ee.Terrain.slope(dem_mean)

# Because the composite has 1 degree pixel scale, the slope calculation
# is essenstially meaningless and difficult to even display (you may need to
# zoom out to see the individual 1 degree pixels).
m.add_layer(dem_comp_slope, {'min': 0, 'max': 0.3}, 'Slope')

# We can use ee.Image.reproject to force the slope calculation and display
# the result with a reasonable scale of 30 m on WGS84 CRS, for example.
slope_scale = ee.Terrain.slope(dem_mean.reproject(crs='EPSG:4326', scale=30))
m.add_layer(slope_scale, {'min': 0, 'max': 45}, 'Slope w/ CRS and scale')

# To more precisely control the reprojection, you can use the "crsTransform"
# parameter instead of the "scale" parameter or set the projection according to
# a reference image. For example, here the input composite image for the slope
# function is set to match the grid spacing and alignment of the NASADEM image.
nasadem_proj = dem_1.projection()
dem_mean_reproj = dem_mean.reproject(nasadem_proj)
slope_ref_proj = ee.Terrain.slope(dem_mean_reproj)
m.add_layer(slope_ref_proj, {'min': 0, 'max': 45}, 'Slope w/ reference proj')
display('Reference projection', nasadem_proj)
display('DEM composite projection', dem_mean_reproj.projection())

# An alternative method for changing the projection of image composites
# (not accepting the default WGS84 CRS with 1 degree pixel scale) is to
# explicitly set the default projection using ee.Image.setDefaultProjection,
# which will not force resampling, like ee.Image.reproject will.
dem_mean_proj = (
    ee.ImageCollection([dem_1, dem_2]).mean().setDefaultProjection(nasadem_proj)
)
slope_proj = ee.Terrain.slope(dem_mean_proj)
m.add_layer(
    slope_proj, {'min': 0, 'max': 45}, 'slope w/ default projection set'
)
m