diff --git a/src/tgp.cpp b/src/tgp.cpp
--- a/src/tgp.cpp
+++ b/src/tgp.cpp
@@ -248,16 +248,41 @@ static height_t TGPGetMaxHeight()
  */
 static amplitude_t GetAmplitude(int frequency)
 {
-	/* Base noise amplitudes (multiplied by 1024) and indexed by "smoothness setting" and log2(frequency). */
-	static const amplitude_t amplitudes[][7] = {
+	/* Base noise amplitudes (multiplied by 1024) and indexed by "smoothness setting" and log2(frequency).
+	 * Used for maps that have their smallest side smaller than 512. */
+	static const amplitude_t amplitudes_small[][10] = {
 		/* lowest frequency ...... highest (every corner) */
-		{16000,  5600,  1968,   688,   240,    16,    16}, ///< Very smooth
-		{24000, 12800,  6400,  2700,  1024,   128,    16}, ///< Smooth
-		{32000, 19200, 12800,  8000,  3200,   256,    64}, ///< Rough
-		{48000, 24000, 19200, 16000,  8000,   512,   320}, ///< Very rough
+		{60000, 2273, 4142, 2253, 421, 213, 137, 177, 37,  16}, ///< Very smooth
+		{50000, 2273, 4142, 2253, 421, 213, 137, 177, 37,  61}, ///< Smooth
+		{40000, 2273, 4142, 2253, 421, 213, 137, 177, 37,  91}, ///< Rough
+		{30000, 2273, 4142, 2253, 421, 213, 137, 177, 37, 161}, ///< Very rough
+	};
+
+	/* Base noise amplitudes (multiplied by 1024) and indexed by "smoothness setting" and log2(frequency).
+	 * Used for maps that have their smallest side equal to 512. */
+	static const amplitude_t amplitudes_middle[][10] = {
+		{55000, 2273, 5142, 253, 2421, 213, 137, 177, 37,  16}, ///< Very smooth
+		{45000, 2273, 5142, 253, 2421, 213, 137, 177, 37,  61}, ///< Smooth
+		{35000, 2273, 5142, 253, 2421, 213, 137, 177, 37,  91}, ///< Rough
+		{25000, 2273, 5142, 253, 2421, 213, 137, 177, 37, 161}, ///< Very rough
 	};
-	/*
-	 * Extrapolation factors for ranges before the table.
+
+	/* Base noise amplitudes (multiplied by 1024) and indexed by "smoothness setting" and log2(frequency).
+	 * Used for maps that have their smallest side bigger than 512. */
+	static const amplitude_t amplitudes_large[][10] = {
+		/* lowest frequency ...... highest (every corner) */
+		{55000, 2273, 5142, 253, 421, 2213, 137, 177, 37,  16}, ///< Very smooth
+		{45000, 2273, 5142, 253, 421, 2213, 137, 177, 37,  61}, ///< Smooth
+		{35000, 2273, 5142, 253, 421, 2213, 137, 177, 37,  91}, ///< Rough
+		{25000, 2273, 5142, 253, 421, 2213, 137, 177, 37, 161}, ///< Very rough
+	};
+
+	/* Make sure arrays cover all smoothness settings. */
+	assert_compile(lengthof(amplitudes_small)  == TGEN_SMOOTHNESS_END);
+	assert_compile(lengthof(amplitudes_middle) == TGEN_SMOOTHNESS_END);
+	assert_compile(lengthof(amplitudes_large)  == TGEN_SMOOTHNESS_END);
+
+	/* Extrapolation factors for ranges before the table.
 	 * The extrapolation is needed to account for the higher map heights. They need larger
 	 * areas with a particular gradient so that we are able to create maps without too
 	 * many steep slopes up to the wanted height level. It's definitely not perfect since
@@ -269,10 +294,20 @@ static amplitude_t GetAmplitude(int freq
 	static const double extrapolation_factors[] = { 3.3, 2.8, 2.3, 1.8 };
 
 	int smoothness = _settings_game.game_creation.tgen_smoothness;
+	int smallest_size = min(_settings_game.game_creation.map_x, _settings_game.game_creation.map_y);
 
-	/* Get the table index, and return that value if possible. */
-	int index = frequency - MAX_TGP_FREQUENCIES + lengthof(amplitudes[smoothness]);
-	amplitude_t amplitude = amplitudes[smoothness][max(0, index)];
+	int index;
+	amplitude_t amplitude;
+	if (smallest_size < 9) { // Smallest map side is less than 2^9 == 512.
+		index = frequency - MAX_TGP_FREQUENCIES + lengthof(amplitudes_small[0]);
+		amplitude = amplitudes_small[smoothness][max(0, index)];
+	} else if (smallest_size == 9) {
+		index = frequency - MAX_TGP_FREQUENCIES + lengthof(amplitudes_middle[0]);
+		amplitude = amplitudes_middle[smoothness][max(0, index)];
+	} else {
+		index = frequency - MAX_TGP_FREQUENCIES + lengthof(amplitudes_large[0]);
+		amplitude = amplitudes_large[smoothness][max(0, index)];
+	}
 	if (index >= 0) return amplitude;
 
 	/* We need to extrapolate the amplitude. */